Cao and Zhang totaled 486.78 points in the six-dive final Monday, spoiling the medal hopes of Brits Tom Daley and Peter Waterfield, who were shut out.
German Sanchez and Ivan Garcia of Mexico won the silver with 468.90.
Nick McCrory and David Boudia of the U.S. took the bronze with 463.47.
Daley and Waterfield led through the first three rounds, but botched their fourth dive and dropped to fourth, where they eventually finished.
