ZnO single-crystalline films were prepared by predepositing a homobuffer layer on Si (100) substrate in a pulsed laser deposition system. The effect of short-time rapid thermal annealing under N-2 and O-2 ambient on the optical property was systematically studied by photoluminescence measurements from 77 K to room temperature. Different from the adverse effect of the O-2-assisted rapid thermal annealing on the optical quality, N-2-assisted rapid thermal annealing can greatly enhance the ultraviolet emission while eliminate the deep-level emission band including separate green, yellow, and orange luminescence peaks. Such ambient-dependent photoluminescence enhancement was attributed to the elimination of oxygen interstitial in the ZnO film.