Objective The study aimed to obtain strain and myocardial work（MV） parameters by non-invasive left ventricular（LV） pressure-strain loop（PSL） and to evaluate effects of anthracycline-based chemotherapy on LV myocardial function at early and middle stage in patients with breast cancer.Methods Thirty breast cancer patients treated by anthracycline-based chemotherapy and 30 controls were recruited and echocardiography were performed before and after1，2，3，4，5 chemotherapeutic cycle （T0，T1，T2 T3，T4，T5）.TDI parameters included S’ of six points in mitral annulus.Speckle tracking imaging（STI） obtain LV global longitudinal strain（GLS），standard deviations and maximal differences of time to peak regional LS（Tls-SD，Tls-dif） in all 18 segments.MW parameters from LV-PSL included global work index（GWI），global constructive work（GCW），global waste work （GWW） and global work efficiency（GWE）.Compare the parameters mentioned above. Results Compared with controls，blood pressure，LVEF，Tei index，TDI parameters，myocardial strain and MW parameters in the chemotherapeutic groups at T0 showed no significant differences（p＞0.05）. Compared with T0，S’-PostSept，S’-Lat，S’-Ant decreased significantly at T4 and T5（P<0.05），while there was no significant difference in the rest of traditional parameters. Compared with T0，GLS reduced significantly at T4 and T5，showing a gradually decreasing trend as the chemotherapy cycle progressed，while Tls-SD and Tls-dif increased significantly at T4 and T5（p＜0.05）. Compared with T0，GWI, GCW and GWE reduced significantly at T4 and T5，showing a gradual declining tendency as the chemotherapy cycle progressed，while GWW presented gradual inclining tendency（p＜0.05）.Conclusion Though breast cancer patients treated with anthracycline-based chemotherapy did not meet clinical diagnostic criteria for cardiotoxicity in the early and middle stages，they had showed LV dysfunction signs.MW parameters obtained by PSL could assess myocardial work quantitatively and detect myocardial dysfunction sensitively in these patients，which provide a new ultrasound technology for the evaluation of chemotherapy-related cardiac function impairment.