The change of scintillation property of the cerium doped gadolinium pyrosilicate Ce:Gd 2 Si 2 O 7 (Ce:GPS) single crystal by annealing in air was evaluated. The sample crystal was grown by using the floating zone method and the annealing was carried out at 1200 • C in 10 hours. The scintillation characteristics for gamma-rays, the photoluminescence emission and excitation spectra were compared between before and after the annealing process. It was found that the emission spectrum did not change by annealing except the overall intensity, while the excitation spectrum changed with increasing around 240 nm and 290 nm and the excitation band became wider by annealing in air. As a result, the scintillation efficiency for 662 keV gamma-ray increased 6.4% by annealing in air.