Objective To explore the correlation between preoperative frailty and postoperative complications in the elderly colorectal cancer patients undergoing radical surgery. Methods A total of 147 elderly patients who underwent elective laparoscopic radical surgery for colorectal cancer in the Affiliated Tumor Hospital of Guangxi Medical University from May to August 2021 were selected as the research subjects. The general data questionnaire, the grading standard of the American Society of Aneshesiologists (ASA) and the Tilburg frailty index (TFI) were used to investigate the patients′ frailty and grading. At the same time, the patients′ complications were recorded. Data analysis was performed using SPSS statistics 26.0. According to the data type, χ² test was used for comparison between groups. Binary logistic regression was used to analyze the risk factors of complications, and Spearman rank correlation was used to analyze the correlation between preoperative frailty and postoperative complications. Receiver operating characteristic (ROC) curve was used to evaluate the predictive performance of preoperative frailty assessment, predictive value of ASA classification and combined application on postoperative complications. Results Logistic regression analysis showed that activity of daily living (ADL) score, frailty score, and ASA grade were the influencing factors of postoperative complications. Spearman correlation analysis showed that preoperative frailty was positively correlated with postoperative complications (r=0.427). The area under ROC curve of frailty assessment combined with ASA classification is larger than that of frailty assessment alone or ASA classification (AUC=0.797,0.740,0.697). The sensitivity and specificity of joint application were 92.3% and 51.9%, respectively. Conclusion Preoperative frailty is an independent risk factor and predictor of postoperative complications, and preoperative frailty assessment combined with ASA classification can enhance the predictive ability of postoperative complications, providing basis for the patients′ perioperative safety management.