The laminated photoresist sacrificial layer technology and residual stress control in micromirror fabrication were investigated.Pollution problems in electroplating related to the photoresist sacrificial layer were discussed and their solutions were proposed.Through experiments,a new fabrication process is developed to solve the problem that the solvent in upper photoresist penetrates the electroplating base metal layers and dissolves the sacrificial layer to damage middle layer;the thicknesses of two kinds of metal films with different stress states in evaporating and electroplating processes are controlled to remove the residual stress on the surface of a micromirror.Employing these new technologies,the perfect flat micromirror with the size of 620 μm×500 μm×2 μm,and air gap height of 12 μm is fabricated successfully.