GaN crystalline have been grown by low pressure MOCVD. The optical properties and its relationship with the densities of dislocation have been studied. It has been investigated that the photoluminescence spectrum of GaN near interface showed as a broaden emission band and some narrow peaks. The broaden band emission may derive from the transition between shallow donor and dislocation related valance band tail. The excitation power and temperature dependence of photoluminescence intensities have been studied. The experimental results indicate that the narrow emission peaks origin from the deep-bound exciton and the dislocation may act as the bounding center.