She poked home the opening goal from a tight angle before Jill Scott doubled City's advantage with a header.
Ross completed her brace before Georgia Stanway made it 4-0 at the break.
Steph Houghton's foul on Rachel Williams in the box allowed Jess Clarke to pull one back from the spot, only for Isobel Christiansen to add a fifth.
After Christiansen netted with a half-volley from 25 yards, the visitors went close to another when Tessel Middag saw her chip come back off the crossbar in the last of 11 minutes of injury time.
Both sides lost players to injury, as City defender Abbie McManus was stretchered off with an ankle problem and County's Fern Whelan left the field in a neck brace after a collision with Nikita Parris. The Magpies defender was quickly cleared of serious injury.
Victory ensured City maintained a one-point lead at the WSL 1 summit, with Chelsea - who have played a game more than the Sky Blues - temporarily going top earlier on Sunday following a 4-0 win over bottom side Doncaster.
Defeat left Notts sixth in the table with eight points from nine games.
Nott County Ladies manager Rick Passmoor: "We lost it in the first half, when you come to Meadow Lane you expect to face intensity, but we let Manchester City take the game by the scruff of the neck.
"We're disappointed and it's frustrating that the intensity we showed at the start of the second half wasn't there from the start.
"Today was not to our standard, we recognise other teams have stronger teams, but they usually have to come here and fight. Today, City didn't have to do that."
Manchester City Women striker Jane Ross: "We're very happy, it's always difficult to come here, but getting that early goal really settled us and we were able to go on from there.
"We performed really well in the first half, we were clinical with the chances we created and we worked on that. We went out with a game plan and executed it well."
Notts County Ladies: Walsh; Buet, Bassett, F Whelan (Krantz 71), Turner; Moore, Potter, Crichton (Luik 78); White, Williams (A Whelan 78), Clarke.
Substitutes not used: James, Hassall.
Manchester City Women: Bardsley; Bronze, Houghton, McManus (Stokes 63), Campbell; Walsh, Scott, Christiansen (Middag 78); Parris, Ross, Stanway (Duggan 84).
Substitutes not used: Hourihan, Corboz, Tynan, Toone.
Attendance: 1,627
Referee: Rebecca Welch
Match ends, Notts County Ladies 1, Manchester City Women 5.
Second Half ends, Notts County Ladies 1, Manchester City Women 5.
Tessel Middag (Manchester City Women) hits the bar with a right footed shot from the centre of the box.
Offside, Manchester City Women. Megan Campbell tries a through ball, but Nikita Parris is caught offside.
Attempt missed. Jill Scott (Manchester City Women) right footed shot from the left side of the box misses to the right. Assisted by Jane Ross.
Foul by Tessel Middag (Manchester City Women).
Jade Moore (Notts County Ladies) wins a free kick in the defensive half.
Lucy Bronze (Manchester City Women) is shown the yellow card for a bad foul.
Foul by Lucy Bronze (Manchester City Women).
Jessica Clarke (Notts County Ladies) wins a free kick on the left wing.
Foul by Jill Scott (Manchester City Women).
Jo Potter (Notts County Ladies) wins a free kick in the defensive half.
Foul by Demi Stokes (Manchester City Women).
Danielle Buet (Notts County Ladies) wins a free kick in the defensive half.
Foul by Keira Walsh (Manchester City Women).
Ellen White (Notts County Ladies) wins a free kick on the left wing.
Attempt missed. Megan Campbell (Manchester City Women) header from the centre of the box is high and wide to the left. Assisted by Toni Duggan with a cross following a corner.
Corner,  Manchester City Women. Conceded by Megan Walsh.
Attempt saved. Stephanie Houghton (Manchester City Women) right footed shot from the centre of the box is saved in the top left corner.
Corner,  Manchester City Women. Conceded by Ellen White.
Attempt missed. Jessica Clarke (Notts County Ladies) right footed shot from the centre of the box is just a bit too high.
Substitution, Manchester City Women. Toni Duggan replaces Georgia Stanway.
Georgia Stanway (Manchester City Women) wins a free kick on the left wing.
Foul by Danielle Buet (Notts County Ladies).
Jill Scott (Manchester City Women) wins a free kick in the defensive half.
Foul by Jessica Clarke (Notts County Ladies).
Substitution, Notts County Ladies. Aileen Whelan replaces Rachel Williams.
Substitution, Notts County Ladies. Aivi Luik replaces Leanne Crichton.
Substitution, Manchester City Women. Tessel Middag replaces Isobel Christiansen.
Attempt blocked. Nikita Parris (Manchester City Women) left footed shot from the centre of the box is blocked. Assisted by Isobel Christiansen with a cross.
Corner,  Manchester City Women. Conceded by Leanne Crichton.
Georgia Stanway (Manchester City Women) is shown the yellow card for a bad foul.
Foul by Georgia Stanway (Manchester City Women).
Danielle Buet (Notts County Ladies) wins a free kick on the right wing.
Goal!  Notts County Ladies 1, Manchester City Women 5. Isobel Christiansen (Manchester City Women) right footed shot from outside the box to the top right corner.
Substitution, Notts County Ladies. Maja Krantz replaces Fern Whelan because of an injury.
Delay over. They are ready to continue.
Delay in match Fern Whelan (Notts County Ladies) because of an injury.
Attempt missed. Jo Potter (Notts County Ladies) left footed shot from outside the box misses to the left. Assisted by Jessica Clarke.
Substitution, Manchester City Women. Demi Stokes replaces Abbie McManus.
Jane Ross scored two first-half goals as Manchester City inflicted Notts County's heaviest defeat to stay top of the Women's Super League One table.