Abstract： Objective:The clinical data of benign and malignant pulmonary solitary solid nodule (PSSN) and the differences of 18F-FDG PET/CT image characteristics were analyzed to improve the differential diagnosis of benign and malignant PSSN.Methods:Data of 312 patients were examined on 18F-FDG PET/CT in our hospital from January 2015 to June 2023. The pathological results showed that 211 patients with malignant were in the observation group and 101 patients with benign were in the control group.The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of 18F-FDG PET/CT in the diagnosis of benign and malignant PSSN were calculated.The clinical data and imaging characteristics of the two groups were compared. The benign and malignant correlation of PSSN was analyzed.The optimal diagnostic critical value of SUVmax was determined, and ROC curve was drawn to judge the diagnostic value of the model.Results:18F-FDG PET/CT was used to diagnose benign and malignant PSSN with 80.59% sensitivity, 73.33% specificity, 78.85% accuracy, 90.52% positive predictive value and 54.46% negative predictive value. There were significant differences in age and 18F-FDG PET/CT imaging features (maximum nodule diameter, burr sign, lobular sign, pleural involvement, vacuole sign, vascular cluster sign, air bronchial sign and SUVmax) between the two groups(P<0.05).The above data were positively correlated with the benign and malignant correlation of PSSN (P<0.05), and the correlation coefficients were 0.277, 0.301, 0.139, 0.222, 0.265, 0.224, 0.191, 0.133, 0.474, respectively. Binary Logistic regression analysis of the above data and PSSN benign and malignant showed that there were statistically significant differences between benign and malignant PSSN and vacuole sign, vascular cluster sign and SUVmax (P<0.05).The critical value of SUVmax=3.3 was 86.29% sensitivity, 56.20% specificity, 73.08% accuracy, 71.56% positive predictive value and 76.24% negative predictive value in the diagnosis of benign and malignant PSSN.Conclusion:The optimal SUVmax diagnostic critical value 3.3 of PSSN can improve the sensitivity and negative predictive value of 18F-FDG PET/CT in the diagnosis of benign and malignant PSSN. Combined with clinical data and 18F-FDG PET/CT image features, it can improve the differential diagnosis value of benign and malignant PSSN.