The £100m Interchange scheme at Central Square will be built on the former Marland House car park next to the old bus station.
The project is being delivered by the Metro Delivery Partnership, made up of Cardiff council, the Welsh Government, property development firm Richtacres and Network Rail.
Plans include a 14-bay bus interchange within a concourse area, 305 flats in a 22-storey tower block in Wood Street and another nine-storey building fronting Marland Street, a six-storey office block, a 249-space car park.
The bus station project was originally due to open last year but due to changes in the wider plans the project will now be completed in 2021.