Objective To explore the clinical value of ¹⁸F-FDG PET/CT in detection of unexpected gastrointestinal lesions with high uptake. Methods The clinical data of 4 188 patients examined by ¹⁸F-FDG PET/CT were retrospectively analysed. Patients with unexpected gastrointestinal lesions with high uptake suspected of malignant tumors examined by ¹⁸F-FDG PET/CT, and without corresponding clinical symptoms and imaging abnormalities were selected. Forty-five out of 4 188 patients were enrolled, and the results of PET/CT examinations were compared with pathological findings. Results Unexpected gastrointestinal lesions with high uptake were detected in 45 out of 4 188 patients (1.1%). Among the 45 patients, 40 were confirmed by pathological examinations, and the other 5 were lost to follow up. Among the 40 patients, there were 23 cases (57.5%) of malignant lesions, 2 cases (5%) of benign lesions (precancerous lesions) and 15 cases (37.5%) of inflammatory lesions. SUVmax of gastrointestinal tumors group (9.8±4.5) was significantly higher than that of inflammatory lesions group （6.5±2.5）(P<0.05). Conclusion The possibility of unexpected gastrointestinal lesions with high uptake detected by ¹⁸F-FDG PET/CT to be malignant ones is higher, and attention should be paid to the early detection and timely treatment of gastrointestinal tumors without symptoms.