The optomechanical structue of 300mm aperture visible light rough tracking and imaging lens was designed for a certain developing ground base optical telescope. The concave mirror structure contouring the rear surface was optimized and the primary mirror weight was reduced by 41.2%. Aiming at the deficiencies of the conventional cementing structure, the new primary mirror supporting structure with elastic compression was adopted. The Patran finite element method (FEM) simulation software was adopted to analyze the accuracy of the primary mirror surface figure with supporting structure at different tilt angle positions and different temperatures. The installation and test scheme was designed, Zygo interferometer was used to test the accuracy of the primary mirror surface figure with supporting structure indoor; and the test result of the surface figure is 0.04λ (RMS), the design reference value of the visible light wave length λ is 0.633 nm and the wavefront aberrations of the optical system both for longfocus lens and shortfocus lens are 0.132λ (RMS). The test results of the indoor collimator star test, resolution test and outdoor polaris imaging test indicate that the system imaging quality meets the telescope requirement. The results verify the reasonability of the new primary mirror supporting structure and lens optomechanical structure design, which provides the design basis and technical path for developing the optomechanical structure of similar lenses.