光栅拼接法是目前制作大尺寸平面衍射光栅的重要方法之一，而拼接误差是评价拼接光栅是否能够使用的重要指标之一。实时定量测量拼接误差，能够实现对拼接误差的自动闭环调整，通过实时指导拼接提高光栅拼接的精度。建立了衍射波前与光栅拼接误差关系的数学模型，分析了干涉仪测量光栅拼接误差的原理，用ZYGO干涉仪实现拼接光栅0级及-1级衍射波前的数字化定量提取，分析并计算了拼接误差波前，得到五维拼接误差的数值解。利用拼接光栅-2级的衍射波前验证五维拼接误差结果的准确性，实验结果表明由0级、-1级、-2级拼接波前计算的拼接误差具有较好的一致性，为利用波前检测光栅拼接误差并实现自动化闭环调整提供了理论指导。

Mosaic grating is one of the most important methods for fabricating large-size plane diffraction gratings, and mosaic error is an important index to evaluate whether the mosaic grating can be used. Therefore, the real-time quantitative measurement of mosaic error can realize automatic closed-loop adjustment and improve the accuracy of mosaic grating fabrication. The mathematical model of the diffraction wavefront and the mosaic error of the grating is established and the mosaic error is analyzed. The diffraction wavefront of the mosaic grating at the zero-order and the negative first-order is extracted quantitatively by using a ZYGO interferometer. The numerical solution of five dimensional error is calculated by analyzing the mosaic error wavefront, and its accuracy is verified by the negative second-order diffraction wavefront. The experimental results show that the mosaic error of the gratings at the zero-order, the negative first-order and the negative second-order is consistent with each other, which provides theoretical guidance for measuring mosaic error by wavefront and realizing automatic closed-loop adjustment.