Objective:To summarize the clinical characteristics and risk factors of acute rejection(AR)of transplanted pancreas and kidney after simultaneous pancreas-kidney transplantation(SPK)and explore the effects of AR on the survival of transplanted pancreas, kidney and recipients.Methods:From September 2016 to July 2022, the relevant clinical data were retrospectively reviewed for 218 recipients undergoing SPK.According to whether or not AR occurred after SPK, they were assigned into two groups of AR(n=53)and non-AR(n=165). The relevant clinical data were compared for two groups of donors and recipients and the risk factors of AR analyzed by binary Logistic regression.Kaplan-Meier method was employed for comparing the survival rates of recipients/transplanted pancreas and kidneys in two groups.Results:A total of 53 cases(24.3%)developed ARs of transplanted pancreas(n=31, 14.2%)(5 of 2 ARs), transplanted kidney(n=15, 6.9%)(1 of 2 ARs)and transplanted pancreas & kidney AR(n=11, 5.0%)(2 of 2 ARs). Tacrolimus blood levels in AR and non-AR groups were(5.8±1.2)and(6.3±1.6)μg/L and failed to attain targets in 36(67.9%)and 78(47.3%)cases.During follow-ups, the incidence of pneumonia and urinary tract infections in AR group versus non-AR group were[43.4%(23/53)vs.27.3%(45/165)and 39.6%(21/53)vs.18.8%(31/165)]and the differences were statistically significant( P=0.028 & 0.002). The results of multifactorial regression analysis revealed that sub-optimal blood level of tacrolimus was an independent risk factor for an occurrence of AR in grafts of SPK recipients( OR=2.254, 95% CI: 1.167-4.353, P=0.016). Comparisons of 1/5-year postoperative survival rates between recipients in AR and no-AR group(98.1% vs.93.9% and 92.1% vs.92.4%)indicated that the differences were not statistically significant( P=0.233 & 0.806). Through comparing 1/5-year survival rates of transplanted pancreas in AR and non-AR groups(94.3% vs.100%, 89.4% vs.98.6%), the differences were statistically significant( P=0.003 & 0.004). And 1/5-year survival rates of transplanted kidneys in AR and non-AR groups(92.5% vs.100% and 90.2% vs.100%)were compared and the differences were statistically significant(all P<0.001). Conclusions:The incidence of AR is higher in transplanted pancreas and kidney after SPK.And the incidence of pneumonia and urinary tract infection is higher in AR group than that in non-AR group.Sub-optimal blood level of tacrolimus is an independent risk factor for the occurrence of AR.The 1/5-year survival rates of transplanted pancreas and transplanted kidney are lower in AR group than those in non-AR group.It has some effect on the survival of transplanted pancreas and kidney.