Objective To investigate the inhibitory effect and its mechanisms of TLSFJM (JM acute T leukemia cell line derived suppressor factor) on allograf t rejection of small bowel t ransplantation in rat , and to compare the effect s and complications of TLSFJM with those of FK506. Methods One hundred male Brown Norway (BN) rats and 100 Lewis(L EW) rat s were t reated as donors and recipient s of small bowel t ransplantation , respectively. Then they were divided into five groups according to the dose of administ ration of TLSFJM and/ or FK506 : small bowel transplantation group (SBT group) ; large dose of FK506 〔0. 5 mg/ ( kg ·d) 〕group ; small dose of FK506 〔0. 25 mg/ (kg ·d) 〕group ; TLSFJM 〔10 U/ ( kg ·d) 〕group ; TL SFJM 〔10 U/ ( kg ·d) 〕associated with small dose of FK506 〔0. 25 mg/ (kg ·d) 〕group. FK506 and TLSFJM were administered through int ramuscular or int raperitoneal injection , respectively. Survival time , body weight , hepatic and renal function and histopathology of recipient s in each group were observed. Results TLSFJM took no damage effect on the recipient s’renal and hepatic functions 7 days after administ ration. When TLSFJM was administ rated associated with small dose of FK506 in small bowel transplantation , it could not only effectively suppress rejection reaction , extend recipient’s survival time , but also decreased the dosage of FK506 and prevented the side effect s. But TLSFJM may not be used as immunosuppressive agent alone for the prevention and treatment of rejection in rat small bowel t ransplantation because the rejection still existed. Conclusion As an effective immunosuppression agent , TLSFJM associated with small dose of FK506 can prolong the survival time of both recipients and graf ting small bowel , relieve intensity of rejection , and prevent the side effect s when high dosage FK506 is administ rated. TLSFJM may be used as a high-efficiency , low-toxicity immunosuppresive agent in small bowel transplantation.