The influence of different annealing atmospheres (vacuum

air

reductive) on the luminescent properties of lead tungstate single crystals (PWO) has been investigated. UV-excited emission spectra and their excitation spectra of the same PWO sample at different annealing conditions were reported. The emission of PWO as grown was weak and dominated by the defect-related red band which is a disadvantage for the scintillation of PWO. The intrinsic blue band was just discernable from the red band. After air annealing

the luminescence intensity was increased enormously and the green band was turn into the prominence of the emission spectra. It suggested that the green emission originate from some local excess oxygen defects

such as (WO

4

2-

+O

i

) centers (here O

i

means interstitial oxygen atom). After subsequently vacuum annealing

the emission intensity was dropped again

and the increase of 420nm excitation in the excitation spectra of the red band emission was remarkable. The color center around 420nm is harmful to the radiation hardness of PWO and should be avoid. It suggested all the unfavorable factor after vacuum annealing is caused by the increase of the concentration of oxygen vacancy V

o

since the oxygen in the lattice can diffuse outward through the surface when annealing in vacuum under high temperature. So air annealing which decrease the concentration of V

o

is a good method to improve the luminescence properties in full scale.In addition

the splitting of 310nm excitation band into two sharp excitation peaks around 305nm and 320nm was observed for the first time when another PWO sample was investigated after vacuum annealing. With the increasing of V

o

concentration

305nm peak lowered while 320nm peak heightened. It suggested that 305nm excitation is corresponding to the excitation of intrinsic excitons while 320nm excitation is corresponding to the bound exciton related to V

o

-defects.