Abstract: 【Objective】 This study aimed to research the histochemical characteristics and effect of Insulin-like factor 3（INSL3） on the development of Tan sheep testis.【Method】 The testicular histochemical characteristics were compared by special staining,immunohistochemistry,immunofluorescence and morphometric statistical software between the newborn and 35-day-old Tan sheep.【Result】 Compared with the newborn Tan sheep,the testicular tissue of the 35-day-old Tan sheep developed obviously. The positive reaction of AB staining on the basal lamina of seminiferous tubule and the PAS staining of gonocytes were increased prominently,and there were abundant collagen fibers in interstitial tissue. The INSL3 expressed decreased in gonocytes,Sertoli and peritubular myoid cells of 35-day-old Tan sheep testis compared with those at newborn from the results of immunohistochemistry combining with immunofluorescence. The results also showed that the expression in Leydig cells decreased with age.【Conclusion】 Overall,the metabolism of acid glycogen was superior to other carbohydrate components during the testis development of Tan sheep from birth to 35 days of age,and the formation of reticular fibers was earlier than that of collagen fibers. The decrease of INSL3 was consistent with the gradual decrease of FLCs numbers. This study could provide a reference for the study on the regulation mechanism of INSL3 in Leydig cell secretory function.