The City Council wants to add an extra 700 spaces to the east of the Seacourt site, which currently has 794 spaces in an attempt to ease congestion.
Proposals include a new waiting area building and increased cycle parking.
The council said it considered relocating to a lower flood-risk zone but had not been able to find a suitable alternative.
A spokesman said: "The proposals respond to the rapid growth that is anticipated in the city centre, particularly the west end regeneration area."
The site, which serves users entering from the west of the city, has been operating for more than 30 years.
Subject to planning consent, work could start in Spring 2016 with the complex anticipated to be open in the Summer of 2017.
A public exhibition is being held at the Assembly Room at Oxford's Town Hall.
There will be a further session on 19 September at the West Oxford Community Centre.
Plans to expand one of Oxford's Park and Rides into the Green Belt have been unveiled.