Abstract: Objective:To study the influences of ureaplasma urealyticum(UU) infection on the structure of testicular tissue and level of testosterone in rats.Methods:Forty clean grade male Sprague dawley(SD) rats were randomly divided into the experiment group A(at 7 d after surgery), experiment group B(at 14 d after surgery, group B), control group C(at 7 d after surgery) and control group D(at 14 d after surgery)10 rats each group.The group A and B were injected with 0.6 ml UU4(1×10⁷CCU/ml) through punctio vesicae, and the group C and D were injected with the same volume of UU liquid medium.At day 7 and 14 after injection, the structures of testicular tissue of all rats were observed by HE staining, the levels of testosterone in the testis interstitial fluid and plasma of all rats were detected by chemiluminescence method.Results:The changes of inflammatory pathology(including the layer and amount of seminiferous tubule spermatogenic cell decreasing, basement membrane lesion, inflammatory cell infiltrating and mature sperms decreasing) in the testis of group A and B were found by HE staining, the inflammatory changes in group B were lighter than those in group A.The structures of testicular tissue in group C and D were normal.The levels of plasma testosterone in group A and B were significantly lower than that in group C and D(P<0.01), the difference of plasma testosterone level between group A and B was not statistically significant(P>0.05).The testosterone level in testis interstitial fluid in group A was significantly lower than that in group B, C and D(P<0.01), the differences of the testosterone levels in testis interstitial fluid between group B, C and D were not statistical significant(P>0.05).Conclusions:UU infection can lead to the pathologic change of testicular tissue and testosterone secretion decrease.With the extension of time, the testicular tissue structure and testosterone level can gradually recover.