Abstract: A new method of data processing for the evaluation of form errors is proposed by improving the deletion point method, in consideration of the geometrical shape and characteristics of the real profile. BFGS formula and quadratic interpolation method is used to establish a common mathematical model. The deletion point range can be controlled self-adaptively by the deletion point formula adopted in the program for calculation. Reliability of deletion point is assured and efficiency of evaluation in the estimation of form errors markedly enhansed.