According to the requirements of astronomical telescopes for Deformable Mirrors (DMs), a silicon unimorph DM with 200 elements were designed and its characteristics were measured. Firstly, the structure model of unimorph DM was developed using finite element method. The influences of the electrode arrangement and the boundary support of the DM on correction capability were investigated. Then, three prototype DMs( annular & simply support， annular & clamped support， and hexagonal & simply support)were fabricated. The influence functions of the fabricated DMs were measured using an interferometer. And the frequency response was measured using a laser Dopplar vibrometer. The simulation and experimental results indicate that the deflection of the actuator is more than 1 μm at 50 V and the resonance frequency of the DM with clamped boundary is about 1 kHz. The DMs have a well correction capability for the first 100 Zernike aberrations. These show that the developed DMs have potential applications for low-cost adaptive optics in astronomy.