Abstract: In order to suppress the local immune response in swine uterus induced by artificial insemination(AI)and to improve the AI application efficiency,the regulative effect of different dosages of heparin(0,100,500,1 000μg/mL)on changes of chemotaxis and phagocytosis of swine polymorphonuclear neutrophils(PMNs)against sperm were observed with the presence of 10%serum in an in vitro culture system.The results showed that the chemotaxis and phagocytosis of swine PMNs against sperm was found to be significantly inhibited by heparin at the dosage of 100-1 000μg/mL(P<0.05 or P<0.01).It is demonstrated that heparin can effectively suppress the immune response in swine uterus induced by AI,and it is prospected to be used as the protectant of swine semen diluents to improve the conception rate of the artificially inseminated female swine.