For treating acute cerebral infarction, we developed a laser thrombolytic system with the second harmonic generation of microsecond Nd:YAG laser, and investigated its effectiveness, safety and mechanisms in animal thrombosis models. The dynamics of laser-induced thrombolysis in a gelatin phantom model was investigated with a high speed camera. The observation revealed that laser irradiation generated a bubble in the gelatin phantom. In vivo thrombolytic efficacy was investigated using animal thrombosis models. Thrombi in the vena cava inferior of rats or in the carotid artery of rabbits were induced by an application of ferric chloride (FeCl₃). Laser irradiation was then carried out through an optical fiber inserted from the femoral vein or artery. Laser irradiation induced significant thrombolysis in the rat thrombosis model. Laser irradiation also resulted in recanalization in the rabbit thrombosis model. One day after the recanalization, neurological disorders, cerebral ischemia and cerebral hemorrhage were not observed. No vascular endothelial damage evaluated by Evans blue staining after laser irradiation was observed. The irradiation of the pulsed green laser can induce bubbles that fragment thrombi without vessel or brain damage.