At present many experimental studies,clinical and epidemiological studies have demonstrated the differences in pain perception between sexes. A female predominance is found in chronic pains(migraine,TMD,fibromyalgia,rheumatalgia,etc) . Also evidences indicate that female are more sensitive to experimental pain(mechanical pain,electrical pain,heat pain,etc) ,and have a lower pain threshold and patience than male. Menstrual cycle is also related to pain perception. Experimental studies also found differences in pain perception and response in rodent. However,different animal research outcomes suggest that many factors contribute to sex differences. The existing studies have not yet come to a same conclusion on the mechanism. The possible factors include biological factors(sex hormones,endogenous analgesic,genes,etc) ,social and psychological factors as well as the interaction between the two.