Objective To explore the effect and distribution of ultrasound on myocardial contractility , left ventricular myocardium was irradiated by low intensity ultrasound in vitro. Methods Eight New Zealand white rabbits were irradiated with 0.75w pulsed ultrasound from the apical region towards the long axis of the left ventricle for 50 minutes. The rabbits were divided into groups A and B according to the pre and post irradiation. The EF value was measured by M-mode ultrasound in the short axis section of the middle left ventricle. The inner myocardial strains of the left ventricular basal segment, the left ventricular middle segment, the apical segment and the whole circumference of the two groups were measured respectively. The strain differences of the corresponding segments of the two groups before and after irradiation were calculated and compared. Results The EF value in group B was higher than that in group A (P < 0.05). The myocardial inner layer strain of left ventricular basal segment, left ventricular middle segment and apical segment in group B was greater than that in group A. the strain difference between the two groups was statistically significant. Conclusion Low dose ultrasound irradiation in vitro could produce significant positive inotropic effect on left ventricular myocardium, and the increase of left ventricular apical segment near the ultrasound emission area was more significant.