Objective To explore the prognostic value of perioperative period prognostic nutritional index (PNI) (pre⁃/post⁃PNI) in predicting the 3 years progression free survival (PFS) and overall survival (OS) in colorectal cancer patients (CRC). Method A total of 153 pathologically confirmed colorectal adenocarcinoma underwent surgery were collected from December 2012 to January 2020 in Hainan hospital of Chinese PLA general hospital, the PNI were calculated and patients were then divided into different subgroups, the survival differences of these subgroups were run by Kaplan⁃Meier analysis and the risk factors for survival were tested by COX proportional hazards model. Result According to the Youden index, taking 48.73 and 45.40 as the cut⁃off points to divide patients into low or high pre⁃PNI and post⁃PNI subgroups respectively, they have a sensitivity at 71.40%, 83.70% and a specificity at 59.60%, 46.20% individually in predicting the survival. The lower pre⁃PNI was more obvious in T3+T4 (P=0.02), M1 (P=0.02) patients; whereas the lower post⁃PNI was more apparent in older ones (P=0.03), both of which were more detectable in big tumor groups (all P=0.04). Both PFS and OS were inferior in lower pre⁃PNI and post⁃PNI ones (all P<0.01). The preoperative period PNIs were risk factor for PFS and OS; however, only the post⁃PNI was of more reliable (PFS: HR=0.31, 95%CI= 0.14-0.69, P<0.01; OS: HR=0.26, 95%CI=0.10-0.69, P=0.01). Conclusion The perioperative period PNI played an important role in predicating the survival for colorectal cancer patients. However, the post⁃PNI was more reliable when compared with the pre⁃PNI, additional studies are still needed in future.