Based on the fabricated and assembled lidar telescope, the structure of its primary mirror subsystem was presented. The effects on the primary mirror surface of the mismatch among the assembling points on the second supporting board and the malfunction of the flexible supporting foot on the first board were analyzed. The optomechanical analysis was conducted through establishing the finite element model of the primary mirror, the analyzing results were compared with the measured wave front map during the assembling. According to the analysis, the mismatch of the assembling points on the second baseplate was the main reason to deform the primary mirror surface. The primary mirror subsystem structure was optimized through integrated optomechanical analysis. And the expected root mean square deformation of the primary mirror should be decreased from 0.3λ to 0.087λ, which meets the specification requirement of 0.15λ.