The influence of F,Y co-doping on the luminescence properties and defects of PbW O4 (PWO) have been investigated by correlated measurements of transmi ssion spectra, light yield, photoluminescence spectra, thermoluminescence and po sitron annihilation lifetime. F doping results in a new luminescence band peaked around 350nm, which gives a significant improvement in luminescence properties of PWO. Meanwhile, Y-dopant efficiently reduces trapping state and accelerates t he scintillation decay process. Compared with the undoped PWO samples, the light yield (100ns) of F,Y co-doped PWO　crystal was increased by a factor of 2.7. Th e main defects (WO3)- and (WO4)3- in PWO crystals for lack of oxygen during growth were investigated. Thermoluminesc ence results show that the defects in PWO crystals increase when annealed in vac uum and these defects can be also suppressed by annealing in air at 600℃.