Objective To evaluate the effects of different concentrations of parecoxib sodium on the rat sperm motility,capacitation and acrosome reaction in vitro.Methods The sperm samples from Sprague-Dawley rat epididymis were collected by Klinefelter diffusion method and randomly divided into 4 groups (n =18 each) using a random number table:control group (group C),and parecoxib sodium 100,500,1 000 μmol/L groups (P1-3 groups).Parecoxib sodium with the final concentrations of 100,500 and 1 000 μmol/L was added to the culture medium.The samples were then incubated for 5 h in an airtight container filled with 5 ％ CO2 at 37 ℃.Then sperm motility was examined in vitro at 37 ℃ and analyzed by the computer-assisted sperm analysis,including the sperm motility ((a + b)％),average path velocity (VAP),straight line velocity (VSL),curvilinear velocity (VCL) and amplitude of lateral head displacement (ALH).The capacitation effect was assessed by using the chlortetracycline staining and phase-contract microscopy.The acrosome reaction was evaluated by coomassie brilliant blue staining.Results The VAP,VSL,VCL and capacitation ability of the sperm were gradually decreased in C and P1-3 groups (P ＜ 0.05).Compared with group C,(a + b)％ in P2,3 groups and ALH in P2 group were significantly decreased (P ＜ 0.05).There was no significant difference in the acrosome reaction between groups (P ＞ 0.05).Conclusion Parecoxib sodium has significant inhibitory effects on the rat sperm motility and capacitation in a dose-dependent manner,while has no effect on the acrosome reaction in vitro.