Objective To study the value of 18F-FDG PET/CT in diagnosis and preoperative staging assessment of breast cancer. Methods A total of 69 cases of patients with suspected breast cancer treated in our hospital were selected for the study and were given 18F-FDG PET/CT before operation. The postoperative pathological results were used as criteria to analyze the reliability and validity of 18F-FDG PET/CT and its consistency with pathological diagnosis in the diagnosis of breast cancer and to analyze the reliability and validity of 18F-FDG PET/CT to preoperative staging. Results The postoperative pathological results of 69 cases showed there were 67 cases of breast cancer, and the results of 18F-FDG PET/CT showed that 65 cases were SUV positive and 4 cases were negative, and the diagnostic sensitivity, specificity and accuracy of 18F-FDG PET/ CT were 97.01%, 100% and 97.10% in the diagnosis of breast cancer, and its consistency with pathological diagnosis was better (κ=0.896). Among 65 cases diagnosed with breast cancer by 18F-FDG PET/CT, postoperative pathological results showed that there were 6 cases in I stage, 35 cases in II stage, 8 in III stage and 16 in IV stage. 18F-FDG PET/ CT showed that there were 7 cases in I stage, 32 cases in II stage, 11 in III stage and 15 in IV stage. The total accuracy of 18F-FDG PET/CT was 89.23% in the diagnosis of preoperative staging of breast cancer. Conclusion 18F-FDG PET/CT has high diagnostic accuracy in breast cancer, and can better evaluate preoperative tumor staging.