Objective To study the effect of cardiac resynchronization therapy (CRT) on the cardiac function and arrhythmias of patients with chronic heart failure and left ventricular systolic dyssynchrony. Methods Thirty-two cases of patients with chronic heart failure and left ventricular systolic dyssynchrony underwent CRT therapy. And LEVESV, LVEDV, LVEF, LVEDD, MRA, LAA, MRA/LAA were detected by echocardiography while the cardiac function was kept stable. Then the left ventricular systolic 12 segment peak time (Ts) was measurements by tissue doppler in all patients, the poor (Ts-maxD) and standard deviation (Ts-SD) were also calculated. The 24-hour ambulatory 12-lead ECG was took postoperation. All the patients were treated by anti-heart failure drugs after CRT pacemeker implantantion. All these indicators were assessed again at 12 weeks later. Results Compared with the previous CRT pacemaker implantation, LVEF, LV dp/dpsignificantly increased (P < 0.05). LEVESV, Ts-maxD, Ts-SD, MRA, MRA/LAA markedly declined (P < 0.05). But no statistical significance was found between the preoperative and postoperative CRT (P>0.05). Atrial premature beats and paroxysmal atrial tachycardia were significantly reduced in the preoperative CRT (P < 0.05). No significant differences were found in atrial fibrillation, ventricular premature beats and paroxysmal supraventricular tachycardia between the preoperative and postoperative CRT (P > 0.05). Conclusion CRT resynchronization therapy can improve left ventricular systolic function, and reduce the MRA and Ts. The mechanism may be associated with the improvement of left ventricular synchrony, reducing mitral regurgitation, and reducing the occurrence of atrial arrhythmias.