【Objective】 This article focuses on how different power laser in vitro irradiation affects the function of myocardial cells and myocardial microcirculation

and explores the feasibility of controlling the function of myocardial cells through pulse laser in vitro irradiation. 【Method】 With multi-mode pulse width modulation (PWM) electrical stimulation output as incentive signal source

makes the laser output various patterns pulse laser with constant intensity and various pulse width. The precordial region of experimental groups of SD rats were irradiated for 10 days at 30 min/day. Myocardial specimens would be obtained after 10 days. Light-microscopy pathological changes of rats myocardial cell and effect of the number and inner-diameter of myocardial capillaries. 【Results】 The myocardial capillaries inner-diameter in 100 mW group (5.7 ± 0.41) were significantly higher than that of control ones (P < 0.001) in the internal layer of myocardium. The density of myocardial capillaries in 30 mW and 100 mW irradiated groups were better than control group (P < 0.05). In 100 mW irradiated group

part of myocardial cells had edema and lymphocytic infiltrates

while 30 mW irradiated group did not show this phenomenon. 【Conclusion】 Using 30 mW and 100 mW pulse laser irradiation in rats precordial significantly increased myocardial capillary density in the internal and middle layer of myocardial

improving myocardial microcirculation. Using 30 mW pulse laser irradiation has good effect without any side effect.