将待测面形表示为多项式的和，通过分别沿x,y向多次平移待检光学元件得到移动前后待测元件面形差，采用最小二乘法拟合多项式系数，得到待检光学元件的绝对面形。推导了多次平移法的理论公式，并进行了仿真实验，模拟了移动次数、移动间隔和采样点数对测量精度的影响。仿真结果表明:待测平面与初始平面残差图的均方根值为5.118×10-13λ，理论误差达到高精度平面面形检测要求。

The precision of flat measured by relative interference is limited by the precision of standard transmission flat. The absolute measurement method can improve the measure precision by removing the error of standard transmission flat. The absolute measurement of plat with multiple translation method is an effective way to test plat surfaces with high accuracy. The surface under test can be expressed by polynomial function. Different surface profile is obtained by orthogonally shifting the tested flat in two directions orthogonal，then the absolute surface is gained by fitting of polynomial coefficients using the least squares. The theory formula of multiple translation method is deduced，and the error caused by number of sampling points, times and interval of translation are analyzed using the simulation. The results of simulation show that the root-mean-square(RMS)of residual figure error is 5.118×10-13 λ.Thus the method can realize high accuracy measurement of flat surfaces.