采用双球面法对立式Fizeau干涉仪的参考球面进行标定以确定由重力、安装夹持力等导致的面形形变量，提高立式光学系统中光学元件的面形检测精度。首先，推导了双球面法标定算法；进而，理论分析和模拟计算了影响检测精度的环境、重力、安装夹持力等因素；最后，利用双球面法对立式Fizeau干涉仪的参考球面进行标定，并利用误差合成理论分析实验结果。实验结果显示，利用双球面法标定F/15的立式Fizeau干涉仪参考面的精度为23 nm。其中，算法本身以及实验操作引起的测量重复性不大于07 nm，包含环境误差时的重复性低于12 nm；重力导致的面形形变约为09 nm，标准镜安装导致的面形形变约为17 nm。结果论证了双球面法具有很高的标定精度；环境对检测精度的影响与干涉腔长度有关，长度增加时影响很明显；立式工作时，重力、安装等因素导致的标准镜参考球面的面形形变很大，在高精度使用前必须进行标定。

The spherical reference in a vertical Fizeau interferometer was calibrated by the two-sphere method to identify the surface deformations induced by gravity, mounting or holding forces to improve the surface measurement accuracy of optical elements in vertical optical systems. First, the algorithm of two-sphere absolute method was deduced. Then, the factors that may influence measurement accuracy, including environment, gravity, mounting or holding forces were analyzed in theory or calculation by simulation. Finally, the spherical reference used in the vertical Fizeau interferometer was calibrated by two-sphere method, and the experimental results were analyzed by the law of error combination. Experimental results indicate that the calibration accuracy by using two-sphere method is 2.3 nm RMS for the spherical reference of F/15 vertical Fizeau interferometer. Among them, the measurement repeatability induced by the method and experimental operation is no more than 0.7 nm, and that is no more than 1.2 nm while environment influences are taken into account, including vibration and temperature. Furthermore, the surface deformation induced by gravity is about 0.9 nm RMS, and that induced by mounting or holding force is about 1.7 nm. In conclusion, two-sphere method is high precise method that can be used in calibrating vertical spherical reference and the influence of environments on measurement is relative to the length of interferometric cavity. The spherical reference must be calibrated before it is used for high precise measurement vertically, for the surface deformation will be remarkable induced by the gravity, mounting or holding forces.