Abstract: Objective：To analyze the correlations of semi-quantitative index, tumor to non-lesion ratio (T/N)in breast specific gamma imaging (BSGI) and clinical features in breast cancer. Methods：Totally 668 patients who underwent BSGI from January 2016 to July 2017 were enrolled. BSGI interpretation was assessed based on visual spectrum analysis and semi-quantitative analysis. The value of T/N in craniocaudal (CC) and mediolateral oblique(MLO) view was respectively obtained and the maximum value was selected for semi-quantitative analysis. Then the T/N value was compared among different pathological status. Results：Among 668 cases, there were 505 of malignant mass and 163 of benign mass, and the T/N value was obtained in all the cases. Analysis of receiver operating characteristic curve (ROC) showed that the sensitivity and specificity in diagnosing breast cancer was 84.53% and 74.02%, respectively, taking critical value of T/N as 1.81, and the AUC was 0.83 (SD=0.844, 95% CI 0.812-0.872). The T/N value was significantly different among patients with different tumor size (P=0.000), Ki-67 expression (P=0.039) and axillary lymph node metastases (P=0.02). Conclusions：The T/N value in BSGI is correlated with tumor size, Ki-67 expression, and axillary lymph node metastases, which can be used in predicting aggressiveness of breast cancer.