【Abstract】 Object: To investigate the effects of ulinastatin(UTI) on renal function and the mechanism of renal protection, when using UTI in donors and recipients in living donor renal transplantation. Method Forty pairs of patients were randomly assigned into two groups：the ulinastatin group(group U) and the control group(group C). one hour before blocking renal artery, the donors in group U were infused ulinastatin 5 KU/kg (dissolved in 50ml saline) for 20 minutes；when the renal blood vessels opening，the recipients in group U were infused ulinastatin 5 KU/kg (dissolved in 50ml saline) for 20 minutes. The donors and recipients in group C received 50ml saline solution in the same way. The serum TXB2，6-keto-PGF1α levels and the TXB2/6-keto-PGF1α were compared before the anesthesia induction (T1), 15 minutes before vessels opening (T2), vessels opening immediately (T3), the end of the operation(T4), 6h after surgery (T5), 24h after surgery (T6) in two groups. The serum creatinine and cystatin C levels were detected and urine volume was recorded at T1, T6 and 48h after surgery (T7) Results Compared with T1 [Group U:TXB2（211±16）,6-keto-PGF1α（26.0±1.6）,TXB2/6-keto-PGF1α（8.1±0.7）,Scr（577±54）,CysC（5.93±1.67），urine output（297±43）;Group C :TXB2（208±15）,6-keto-PGF1α（26.0±1.8）,TXB2/6-keto-PGF1α（8.0±0.3）,Scr（574±36）,CysC（5.92±1.58）,urine output（292±43）], the serum TXB2 levels in two group[Group U:（391±21）,（406±16）,（465±17）,（433±22）,（339±26）; Group C:（417±24）,（443±21）,（503±17）,（485±14）,（424±21）] were significantly increased at the points of T2~T6 (P<0.05)，While the serum TXB2 levels declined from their peaks of T4 , the serum TXB2 levels still higher than before surgery ; the serum 6-keto-PGF1α levels in two group[Group U :（38.4±1.0）,（37.5±1.1）,（35.9±1.1）,（32.2±1.2）,（26.3±1.4）;Group C :（38.5±0.8）,（37.9±0.7）,（28.9±1.7）,（27.5±1.3）,（26.2±1.5）] were significantly increased at the points of T2~T6 (P<0.05)，While the serum 6-keto-PGF1α levels declined from their peaks of T3, the serum 6-keto-PGF1α levels still higher than before surgery (P<0.05); the serum TXB2/6-keto-PGF1α level in two group [Group U :（10.2±0.5）,（10.8±0.4）,（12.9±0.5）,（13.4±0.8）,（12.9±1.2）;Group C :（10.8±0.5）,（11.7±0.4）,（17.5±1.1）,（17.6±0.5）,（16.2±0.8）]were significantly increased at the points of T2~T6 (P<0.05); the serum creatinine[Group U :（324±14）,（188±12）;Group C :（357±19）,（211±16）] and cystatin C levels [Group U :（1.90±0.34）,（1.57±0.20）;Group C :（2.27±0.36）,（1.86±1.24）]in two group were significantly increased in T6 and T7 (P<0.05); urine output[Group U :（8330±421）,（5584±825）;Group C :（8065±669）,（5389±721）] significantly increased in T6 and T7 (P<0.05). Compared with C ,the serum TXB2 levels were significantly declined at the points of T2~T6 (P<0.05);the serum 6-keto-PGF1α levels were significantly declined in T4 and T5(P<0.05);the serum TXB2/6-keto-PGF1α levels were significantly declined;the serum creatinine and cystatin C levels were significantly declined in T6 and T7 (P<0.05); urine output increased in T6 and T7, but there was no significant difference (P>0.05).Conclusion UTI can protect renal function during related donor kidney transplantation, which is related to effectively correct the TXA2/PGI2 proportional unbalance to improve renal blood perfusion.