High-resolution space remote sensor needs large system aperture, but it is hard to fabricate one single mirrors with large aperture, furthermore, limited by size of the rocket, and aperture of primary mirror can only be enlarged in a certain degree. This problem is solved by using several segmented mirror to build one large mirror. But surface error and radius mismatch of segmented mirror will decrease performance of the whole system. Substitute recent methods which use actuators of segmented mirrors to correct these errors, a new method using deformable mirror that lies in the exit pupil corrects those errors is proposed and simulation has been done. Simulation results show that this method can correct those errors very well in certain cases.