MEMS Fabry-Perot tunable filter is obviously notable because of its mass production and easy integration. Membrane is the key portion of the filter as its structure directly affects the filter’s performance and fabricating difficulty. In this paper, some typical membrane structures with different dimensions are simulated. Through making finite element analysis to these simulations and comparing of the results, we find out useful information such that foldaway and spiral cantilevers can achieve longer length in the same membrane area; the longer cantilevers are, the smaller electrostatic force is needed, accordingly the bias voltage is lower and the membrane curvature is smaller, etc. Then we use the information to analyze some important factors affecting membrane’s physical and optical performance and make an optimum design.