在高功率激光系统中，大口径元件的中频波前影响系统的安全运行，中频波前均方根(PSD1)是用来评价中频波前质量的关键参数。由于大口径干涉仪在系统传递函数(STF)上不能完全满足中频波前的检测要求，提出采用小口径高分辨率干涉仪检测的统计分析方法，建立了统计理论模型，分析了测量不确定度。建立了子区域PSD1检测装置，提出了子区域倾斜补偿法，提高了检测精度。理论及实验结果表明针对400 mm×400 mm分析区域，子区域数量设置为4×4，置信水平为95.4%时，测量不确定度为±0.266 nm。该方法与大口径干涉仪检测法的对比实验表明，400 mm×400 mm分析区域内检测结果偏差小于5%。子区域统计分析法是对大口径干涉仪检测法的有益补充，对先进光学制造工艺的优化具有重要的参考价值。

In high-power laser system, mid-spatial-frequency wavefront of large flat influences safety of the system and root mean square of mid-spatial-frequency wavefront (PSD1) is used to evaluate corresponding wavefront. Because large-aperture interferometer can′t fully meet the demand of the need of system transfer function (STF) for testing mid-spatial-frequency wavefront, a statistical method based on small-aperture interferometer is proposed, and the uncertainty is analyzed. Testing system is set up, and the sub-region tilt compensating method is developed. Testing resolution is improved. Theoretical and experimental result shows that for 400 mm×400 mm analyzing region, when the number of sub-region is set to 4×4 and confidence level is 95.4%, uncertainty is ±0.266 nm. In comparing test with large-aperture interferometer, deviation between two methods in analyzing region of 400 mm×400 mm is less than 5%. Sub-region statistical analyzing method is a useful compensation for large-aperture testing method and plays a critical role for optimization of advanced optical fabrication technics.