Objective To evaluate the systolic function of the left ventricle by two dimensional speckle tracking imaging (2D-STI) before and after aortic valve replacement.Methods Forty-seven patients undergoing aortic valve replacement because of severe aortic valve stenosis were enrolled and divided into two groups:the eject fraction (EF) ＞ 50％ (group A),and the eject fraction ＜ 50％ (group B).All of them underwent thoracic echocardiographic examination 1-3 days before the surgery and 1 week after the surgery.The strains and strain rate of all segments of the left ventricle were obtained by two dimensional speckle tracking imaging.Meanwhile,the EF and the left ventricular mass index (LVMI) were obtained before and after the surgery.Results Compared with pre-operation,the EF in group A was decreased from (62.57 ± 5.45) ％ to (57.69 ± 4.42) ％ (P ＜ 0.05),and there was no significant difference in group B (P＞ 0.05).In group A,the LVMI was decreased significantly from (177.59 ± 5.91) g/m2 to (169.17 ±5.27) g/m2 (P ＜0.05),also decreased significantly in group B,from (172.79 ±9.39) g/m2 to (165.03 ± 9.75) g/m2(P ＜ 0.05).After the surgery,the systolic longitudinal strains and strain rates in the basal and middle segments of the anteroseptum and the basal segment of the anterior wall showed no significant difference between the two groups (both P ＞ 0.05),and the systolic longitudinal strains and strain rates in all the other segments of the left ventricle were significantly increased (all P ＜ 0.05).Conclusion After the aortic valve replacement,during the perioperative period,LVMI is significantly decreased,while the EF has no significant change,but the systolic longitudinal strain and strain rate in many segments of the left ventricule are increased greatly,suggesting that the left ventricular function turns better.