Abstract: Mirror surface reflecting high power laser would be deformed by the pressure of the coolant in a liquid cooling mirror system. In order to eliminate the impact of pressure and vibration of cooling water of micro channel mirror on the stability of the output beam and the space limitation of micro channel to flow of water, an outside cooling mirror with heatpipe was designed. In the same conditions, solid mirror, micro channel water cooled mirror and heatpipe outside cooling mirror are simulated by ANSYS program. The time-varying thermal deformation of the mirrors under heat absorption of 12 W/cm2 and continuous work of 60 s is obtained. The results indicate that the maximal mirror surface deformation of z-axis between peak and valley of solid mirror, micro channel water cooled mirror and h