Objective Intraoperative localization of gastrointestinal lesions has been an important issue in laparoscopic surgery, we have developed a new magnetic tracer technique for preoperative endoscopic marking. This paper is to evaluate the feasibility and safety of this method. Methods From April to June in 2019, in a preliminary study, 8 patients with gastric (n=3) or colorectal (n = 5) tumors underwent endoscopic magnetic marking before laparoscopic surgery. Now, we report the relevant informations of preoperative marking and operation. Results All 8 lesions were marked successfully in endoscopy center by clapping magenets. In subsequent laparoscopic surgery, the other magnets inserted into the abdominal cavity were quickly combined with the magnets in the gastrointestinal tract to successfully locate the lesions. The average time of endoscopic marking was 5.75±2.45 minutes, and the average time of intraoperative localization was 1.94±0.56 minutes. All patients underwent laparoscopic tumor resections with accurate localization. The average proximal and distal resection margins of colorectal tumors were 105 and 74 mm respectively. No adverse complications occurred. Conclusion Magnetic tracer technique of gastrointestinal lesions is simple and safe for laparoscopic localization, which not only can be performed without additional equipment, but has a series of advantages, such as accurate localization, less intraoperative cooperation and fewer hospital infection.