Objective To explore the correlation between ECG left bundle-branch block and left ventricular mechanical dyssynchrony by echocardiography in patients with chronic heart failure. Methods A retrospective analysis was conducted on 39 patients with chronic heart failure admitted to our hospital from June 2018 to June2019. They were divided into “true”LBBB（t-LBBB） and “false”LBBB（f-LBBB） group according to QRS morphology. A comparison was made according to the two groups. Results Patients with “true”LBBB（n=21） had a greater left ventricular mechanical dyssynchrony compared with patients with “false”LBBB（n=18）（p<0.01）.Conclusions Left ventricular mechanical dyssynchrony detected by echocardiography is greater in patients with“true”LBBB than in those with“false”LBBB.