Active correction means for thin mirror surface could be divided into force correction and moment correction. In order to enrich and improve the active support technology in active optics, calibration in free harmonic vibration modal was provided to evaluate the capacity of moment correction for thin mirror. First,the methods of wave front fit-ting and horizontal corrective force solving for moment correction model in the free harmonic vibration modal were pro-vided. Then,as an analysis object,FE model of a thin mirror with the aperture of 400mm was built and the horizon-tal corrective forces were calibrated in detail. Last,the coefficients of corrective forces were solved in a load case,and the residual error of surface was 5.4nm after corrected. In conclusion, such active moment correction for thin mirror was effective, and the calibration in free harmonic vibration modal was reasonable. So the study provided an important value to moment correction for mirror surface.%薄镜面面形的主动校正方式主要分为力校正和力矩校正两种。在技术较为成熟的力校正基础上，为丰富和完善主动支撑技术，提出利用自由谐振模式定标法分析薄镜面的力矩校正能力。首先分析了薄镜的力矩校正在自由谐振模式下的波前拟合和水平校正力的定标计算方法。然后，以一块口径400mm薄镜作为分析对象，建立了相应的有限元模型，完成了该反射镜水平校正力的定标计算。最后，针对某一工况镜面变形，求解了相应的校正系数，通过计算，校正后镜面面形残余误差为5.4nm，校正效果明显。结果表明，薄镜面的力矩主动校正是可行的，提出的自由谐振模式定标计算方法也是合理的，为进一步开展力矩主动校正技术的研究提供了一种参考。
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