在高精度光学元件领域，特别是大口径的平面光学元件，随着对测试精度和口径要求的提高，重力变形成为其不可避免的问题。介绍了立式斐索型干涉仪的系统设计和多点可调支撑方法的变形理论，通过有限元分析（FEM），优化得到了合理的支撑结构。采用液面基准，在300 mm口径的立式斐索型干涉仪上进行了平面的重力变形校正。与三平面法检测结果比较，两者的残差峰谷（PV）值为10.20 nm，均方根（RMS）值为1.56 nm。

In the field of high-precision optical elements, especially the planar optical elements with large aperture, the deformation by gravity becomes an inevitable problem with the improvement of requirements for higher measuring accuracy and larger aperture. The system design of vertical Fizeau interferometer and the deformation theory of multi-point adjustable support method were introduced.By finite element method (FEM) analysis, the reasonable support structure is optimized and derived. Calibration of deformation of flat by gravity was obtained on 300-mm-diameter vertical Fizeau interferometer with liquid surface datum. Comparing it with detection result by three-flat method, the residual between two methods can reach 10.20 nm for peak valley (PV), and 1.56 nm for root mean square (RMS).