Objective The objective of this study was to evaluate the prognostic value of postoperative prognostic nutritional index(p-PNI)in the prognosis of colorectal cancer patients.Methods Retrospective analytical cases came from 89 patients with radical resection of colorectal cancer confirmed by the pathological section in Nanjing Drum Tower Hospital Suqian City People′s Hospital from August 2009 to August 2012.The p-PNI was calculated based on the results of blood routine and biochemical tests after the first visit to the hospital.The Youden index was calculated using the receiver operating characteristic curve(ROC),and the PNI value combined with the best sensitivity and specificity was used as the threshold for the PNI packet.Kaplan-Meier method was used to study the effect of p-PNI on postoperative prognosis of patients with colorectal cancer.Cox regression model was selected to study the effect of p-PNI on the prognosis of colorectal cancer patients after surgery.Results The p-PNI of 89 cases of colorectal cancer patients was 25.18~60.74(43.81±6.47).The p-PNI in patients(less than 70 years old)was significantly increased when the number of lymph node metastases was less than 4,the preoperative CEA was less than 5ng/mL,and the intraoperative hemorrhage was less than 150mL(P<0.05).When the p-PNI value was 43,the Youden exponent was the largest.Data analysis showed that p-PNI was correlated with age,lymph node metastasis,intraoperative blood loss and preoperative CEA(P<0.05).The survival rate of patients with high p-PNI was higher than that of low p-PNI group(χ2=15.639,P<0.001).Single factor and multivariate analysis confirmed that p-PNI was an independent factor in the prognosis of patients with colorectal cancer(HR=2.179,95% CI:1.057~3.561,P<0.001).Conclusion p-PNI is an independent prognostic factor in patients with colorectal cancer,which is associated with long-term prognosis after surgery.