Micromirrors are used in numerous applications such as optical switching, projection displays, biomedical imaging and adaptive optics. Squeeze film damping is one of the dominant energy loss mechanisms in micromirrors. In this paper, the squeeze film damping of a piston mode micromirror structure is studied. Damping analysis is performed for different material combinations and materials which lower the damping coefflent and improve the quality factor are identified. Dependence of damping on ambient pressure is also analysed. Minimum damping coefficient is obtained when Aluminium is used for centre plate and cantilever beams. The maximum value of von Mises stress is less than the yield strength thus ensuring safe operation of the structure. The modeling and analysis are done using COMSOL Multiphysics 4.3b.