Abstract: The postoperative complications in patients with gastric or colorectal cancer has been common but seriously affecting patients′ recovery and even their life safety. According to the database of China Gastrointestinal Cancer Surgery Union, abdominal infectious complications are the main causes of secondary surgery and postoperative death, which deserve clinical attention. However, the incidence rate of postoperative abdominal infection varies widely from center to center. Due to the lack of nationwide data, it is unable to determine the incidence of abdominal infectious complications reasonably and formulate the corresponding strategies of evidence-based diagnosis and treatment. Therefore, this multi-center prospective cohort study, i.e. prediction of abdominal complication after gastroenterological surgery (PACAGE), aims to investigate the incidence, classification and outcomes of postoperative abdominal infection in patients with gastric or colorectal cancer, to implement the standardization of the complication registration, and to provide necessary data for improving surgical safety, preventing abdominal infection and decreasing the rate of postoperative complications in the future.