Abstract: A 3-DOF flexure optical mount was designed to achieve elastic mounting and precise adjusting for small optics. Its mechanical properties were studied analytically. The mechanical model of the optical mount has been established based on its working principles. The stiffness formulas of each DOF were deduced and validated by finite element analysis (FEA). The mechanical properties influenced by structure parameters were analyzed and the methods to reduce parasitic motions were discussed based on the stiffness formulas. The structure design, parameters optimization, and mechanical performance stimulation were carried out for a mirror plate with clear aperture of 135 mm. The comparative results between analytical studies and FEA show that the relative errors are 5.5% and the stiffness formulas have sufficient accuracy. The analysis results also demonstrate that the analytical model and calculations are correct. The conclusions of mechanical analysis of the 3 -DOF flexure optical mount have theoretic significance for its structure design, mechanical performance analysis, and parameters optimization.