Objective: To study the effect of substance P on the expression of protease activated receptors(PARs) in peritoneal macrophages from normal and allergic mice. Methods:Allergic mice were induced by intraperitoneal injection of ovalbumin(OVA). Mice were divided into normal saline, 0.2 μg/ml, 2.0 μg/ml, 20.0 μg/ml and 200.0 μg/ml SP groups respectively, with 6 mice in each group. The expressions of PARs on the surface of peritoneal macrophages were then analyzed by flowcytometry. Results:PAR-1, PAR-2, PAR-3 and PAR-4 expressions on the surface of peritoneal macrophages were all significantly decreased in allergic mice compared with normal mice(P < 0.01). Substance P had no significant influence on expressions of PARs in macrophages(P > 0.05). Conclusion:The intraperitoneal injection of substance P had no effect on the expressions of PARs in macrophages from mouse peritoneum, but OVA treatment did.