〔Abstract〕 Objective To investigate the value of left ventricular global longitudinal strain(LVGLS) in predicting early chemotherapy related cardiotoxicity in breast cancer patients after chemotherapy. Methods Eighty-six breast cancer patients were enrolled in this study and received 6 cycles of doxorubicin +cyclophosphamide. Conventional echocardiography parameters were measured before chemotherapy(T0), immediately after chemotherapy(T1), 6 months(T2) and 12 months after chemotherapy(T3). LVGLS was obtained by 2D speck tracing imaging(2D-STI), and the relative change of LVGLS(△LVGLS) was calculated at T1. With the occurrence of cardiotoxicity as the clinical outcome, receiver operating characteristic(ROC) curve was plotted.The parameters were analyzed at T1 to evaluate the value of △LVGLS in predicting cardiotoxicity. Results (1) Although the change in LVEF was not different between T0 and T1(P>0.05), LVEF decreased significantly at T2 and T3(P<0.05).(2) Compared with T0, LVGLS decreased at T1, which was further damaged at T2 and T3(P<0.05).(3) Seven patients(8.1%) developed chemotherapy-related cardiotoxicity. LVGLS and △LVGLS were correlated with cardiotoxicity at T1 stage, and △LVGLS was more significant(r=0.64,P<0.001). ROC curve analysis showed that a △LVGLS>12% at T1 predicted cardiotoxicity, with sensitivity of 92.2%, specificity of 76%, and area under the curve was 0.88. Conclusion The LVGLS decreased earlier than LVEF in breast cancer patients after doxorubicin treatment. △LVGLS>12% is a good predictor of cardiotoxicity in patients with breast cancer.