Objective To study the effects of hyperglycemia on CaSUP>2+/SUP> oscillation of mouse preovulatory oocytes and the expression of tumor necrosis factor-related apoptosis inducing ligand(TRAIL) in granulosa cells. Methods Twenty day old female mice were used to make a hyperplycemia model with streptozocin. Both diabetic and normal agematched control mice received superovulation treatment with 10IU of pregnant mares srum gonadatropin(PMSG) and human chorionic gonadotropin(hCG). CaSUP>2+/SUP> oscillation of germinal vesicle(GV)stage oocytes collected after hCG injection (0 hours, 2 hours, 6 hours and 10 hours) were recorded with two-photon laser scanning microscopy (TPLSM). The expression of TRAIL in cumulus oocyte complesx(COC) was detected by immunofluorescence and Western blotting at 6 hour and 10 hour after hCG injection. Results 1.Faster CaSUP>2+/SUP>oscillation frequency was observed in the oocytes from the hyperglycemia group at 2 hours and 6 hours intervals ( EM>P/EM> <0.05); 2.Intensities for TRAIL positive immunofluorescence reactions and Western blotting staining intensities were stronger in the hyperglycemia groups than that in the control groups at the intervals of 6 hours and 10 hours( EM>P /EM><0.05),respectively. Conclusion Hyperglycemia increased CaSUP>2+/SUP> oscillation frequency of mouse preovulatory oocytes; Hyperglycemia increased express