Several types of laser are used in laser angioplasty and in experimental works to study the effects of laser on blood vessel and blood clot. They differ from each other by a lot of properties mainly in wavelength, energy of the laser and pulse duration. Argon laser, CO2 laser and Nd: YAG laser are used widely in the ablation of atheroma and in the recanalization of occluded vessels. In this study Argon laser (488 nm- 514 nm), Co2 laser (10. 6 μm), doubled frequency Nd: YAG laser (532 nm) and Cw Nd: YAG laser (1.064 nm), have been applied to 100 samples of synthetic blood clot inside a sheep blood vessels. The results showed that all types of these lasers are able to ablate the blood clot grossly. A mathematical model has been also used to study the effects of clot ablation by laser. The results are contrastive depending on the value of the damage function. The highest damage is achieved by argon laser and the lowest damage is by using Cw Nd: YAG laser. Histologically, the results of the study were different according to the type of laser used; argon laser had distractive effects on the blood vessel. CO2 laser wasn’t safe on the blood vessel too. The doubled frequency Nd: YAG laser showed less damaging effects on the blood vessel and Cw Nd:YAG laser appeared to be the safest one on the blood vessel architecture. We concluded from this study that both Cw and doubled frequency Nd: YAG lasers are able to ablate the atheroma effectively without hurting the blood vessel.