主镜面型精度是地基大口径望远镜最关键的技术指标之一。为了研究主镜室以及主镜底支撑和侧支撑系统的重力变形造成的主镜面型误差，介绍了一地基光电望远镜的主镜室及详细的主镜支撑结构，借助于有限元法，建立了主镜，主镜室和支撑结构的详细有限元模型，分析计算了主镜在支撑状态下的镜面变形情况，并通过 ZYGO干涉仪进行了面型检测。计算结果和实测结果对比，说明了主镜室及其支撑结构引入的主镜面型误差大小，同时也验证了有限元模型的正确性。

The primary mirror surface figure precision is a key factor for the large ground-based telescope. In order to study the surface figure error caused by gravity deformations of primary mirror cell, and axial and lateral supporting system, the mirror cell and mirror supporting structures for a telescope were introduced. A precise finite element model of the primary mirror, mirror cell and mirror supporting structure was established by using the finite element method. Deformation of the primary mirror surface under supporting was calculated and the surface figure was tested by ZYGO interferometer. By contrast with the calculated results and tested results, it shows the mirror surface figure error caused by the supporting structures, and verifies the correctness of the finite element model.