Objective To evaluate left ventricular function before and after percutaneous balloon mitral valvuloplasty (PBMV) by echocardiography. Methods Left ventricular function of 80 patients who underwent PBMV were estimated by echocardiography before and after operation. Results Left ventricular end-diastolic volume (EDV), cardiac output(CO), systolic volume (SV)and ejection fraction (EF) significantly increased 1 week after PBMV, but Left ventricular end-systolic volume (ESV) had no change. EF improved as mitral valve area(MVA)increased, But it had no change while the pressure gradient across the mitral valve(PG)reduced. Left ventricular function had no further improvement 3 months after PBMV. Conclusion Left ventricular function of most of the patients was improved as EDV increased after PBMV, especially early stage after PBMV. MVA was the most important factor which influenced the left ventricular function. There was no significant correlation between EF and the PG reduction after PBMV.