The second instalment of the drama has already begun filming in Australia, with Elisabeth Moss reprising her role as detective Robin Griffin.
Christie, who has also appeared in Star Wars: The Force Awakens, said she "could not feel more privileged" to be joining the cast.
The first season of Top of the Lake was broadcast on BBC Two in 2013.
The six-part series won an Emmy award for outstanding cinematography for a miniseries and Elisabeth Moss won a Golden Globe for best actress in a miniseries.
The show is directed and co-written by Jane Campion - one of only four women to have been nominated for the best director Oscar.
Christie, who plays Brienne of Tarth in Game of Thrones and Captain Phasma in Star Wars, will have a major role in the programme.
She said: "Jane Campion has been a major creative influence throughout my life.
"I could not feel more privileged to be working on the next instalment of unique and enthralling drama."
No specific details have been released about the character she will be playing.
Elisabeth Moss, who has also starred in Mad Men and The West Wing, said: "I'm so excited to be back in Australia working with Jane on exploring this wonderful character.
"I can't wait for audiences to see where we take Robin's journey".
David Dencik, Alice Englert and Ewen Leslie will also appear in the the show's second season.
Top Of The Lake: China Girl will pick up four years on from the ending of the first series, and will see Moss's character try to solve a case after the unidentified body of an Asian girl washes up on to Sydney's Bondi Beach.
The new series will be co-directed by Ariel Kleiman and will consist of six hour-long episodes.
Filming for the series commenced in Sydney on Monday, with the show expected to premiere on BBC Two in 2017.
Game of Thrones star Gwendoline Christie is to appear in the new series of Top of the Lake.