With the development of micro-electro-mechanical system (MEMS) based on silicon micromaching technology, it becomes possible to develop a low-cost adaptive optics system to compensate the aberration of laser beams. The effect of thermally induced aberration on laser beam quality is analyzed based on mode coupling theory. The relation between coupling amplitude of ideal and aberrated fundamental mode and Zernike aberration is numerically simulated. An adaptive optics system is presented based on a MEMS deformable micro-mirror to compensate the thermally induced aberration. From the test result, it is explicit that the adaptive system can correct the thermally induced aberration of high power lasers and increase the Strehl ratio to about 80% averagely.