Tri-ortho-cresyl phosphate (TOCP) has been widely used as plasticizers, plastic softeners, and flame-retardants in industry and reported to have a deleterious effect on the male reproductive system in animals besides delayed neurotoxicity.Our preliminary results found that TOCP could disrupt the seminiferous epithelium in the testis and inhibit spermatogenesis,but the precise mechanism is yet to be elucidated.The present study shows that TOCP inhibited viability of rat spermatogonial stem cells in a dose-dependent manner.Compared with control group, TOCP couldnt lead to cell cycle arrest in the cells;the mRNA levels of p21, p27, p53 and cyclin D1 in the cells were also not affected by TOCP.Meanwhile, TOCP didnt induce apoptosis of rat spermatogonial stem cells.After treatment with TOCP, however, both LC3-Ⅱ and the ratio of LC3-Ⅱ/LC3-Ⅰ were markedly increased;autophagy proteins atg5 and Beclin 1 were also increased after treated with TOCP, indicating TOCP could induce autophagy in the cells.Ultrastructural observation under the transmission electron microscopy (TEM) indicated that autophagic vesicles in the cytoplasm containing extensively degraded organelles such as mitochondria and endoplasmic reticulum increased significantly after the cells were treated with TOCP.In summary, we have shown that TOCP can inhibit viability of rat spermatogonial stem cells and induce autophagy of the cells, without affecting cell cycle and apoptosis.