Thermal induced distortion in the gain element is the main obstacle to be overcome in the scaling of solid-state lasers to very high output powers. The method of compensating the aberration by using an intra-cavity adaptive optical system was studied. A MEMS deformable mirror using as the intra-mirror of the solid-state laser could improve the mode and output power of the laser. The effect of the intra-cavity aberration to the beaconing light form out-cavity could be measuredwith a wave-front detector and an adaptive optic system has been used to compensate the aberration. The experimental result shows that the output power is increased nearly 3 times and the beam profiles are improved obviously by closed loop automatic optimization of the adaptive optic system.