This study aimed to evaluate the changes in the left ventricular (LV) myocardial work (MW) in breast cancer patients following chemotherapy by left ventricular pressure-strain loop (LVPSL).A total of 50 patients with newly breast cancer undergoing postoperative adjuvant chemotherapy containing anthracycline were selected. Echocardiography was performed before the treatment (T0), the second (T2) and fourth (T4) cycles of chemotherapy, and 3 (P3 m) and 6 (P6 m) months after the end of chemotherapy. The standard dynamic images of the required sections were collected. After off-line analysis, the routine, global myocardial strain, and global MW parameters were obtained, and the average regional MW index (RMWI) and regional MW efficiency (RMWE) at three levels of LV were calculated.Compared with those at T0 and T2, the global work index (GWI), global constructive work (GCW), global work efficiency (GWE), and global longitudinal strain (GLS) gradually decreased and global wasted work (GWW) gradually increased at T4, P0, and P6 m. The mean RMWI and RMWE of the three levels of LV exhibited a gradually decreasing trend at T4, P0, and P6 m compared with those at T0 and T2. The GWI, GCW, GWE, mean RMWI, and RMWE (basal, medial, and apical) were negatively correlated with the GLS (r = -0.76, -0.66, -0.67, -0.76, -0.77, -0.66, -0.67, -0.59, and -0.61, respectively), whereas the GWW was positively correlated with the GLS (r = 0.55).The mean RMWI and RMWE are effective parameters to reflect the cardiotoxicity of LV, and LVPSL has certain value in the evaluation of the left ventricular myocardial work (LVMW) during anthracycline treatment and follow-up in breast cancer patients.