The influence of doping with different trivalent ions (La3+，Y3+，Bi3+，Sb3+)on the properties of lead tungstate crystals (PWO) has been investigated. Transmission, emission, positron annihilation lifetime and x-ray photoelectron spectra of different trivalent ions doped and undoped PWO are reported. The scintillation characteristics of the La-doped、Y-doped、Bi-doped、Sb-doped PWO crystals are discussed by comparing with the result of undoped PWO crystal. All the trivalent ions but Bi3+ doping gave a significant improvement in luminescence property of PWO obviously. The defects in PWO crystals caused by trivalent-ion dopants have been studied by means of positron annihilation lifetime and x-ray photoelectron spectra. The results can be stated as follows: La dopant can increase the concentrations of both lead vacancy (VPb) and the low-valent oxygen; Y and Bi dopant can decrease the concentrations of both VPb and low-valent oxygen; and Sb dopant can increase the concentration of VPb but decrease the concentration of low-valent oxygen. We consider that the La ions will replace the lattice Pb2+, the Y and Bi ions will occupy the lead vacancy; and the Sb ions have two valence states (+3 and +5), which will replace the lattice Pb2+ and W6+ ions, respectively.