Mobile rail profile detectors can obtain high-precision three-dimensional image of rail shape with accurate mileage position by measuring the whole section rail profile continually and frequently. However，there is no exiting mature method to use these data for accurate rail grinding. The paper proposes an accurate method for rail grinding based on data measured with high frequency，getting an accurate scheme of rail grinding in the whole test region through fine partition of rail head and segment of mileage after obtaining the curve of grinding amount varying with mileage by comparing the measured profile with the target profile. The method was proved by field test on Beijing-Shanghai high-speed railway of Shanghai Hongqiao Station Line，which achieved accurate rail grinding. Finally，a PSI (profile similarity index) is put forward to evaluate the quality of rail grinding. The results show that PSI can quantify the similarity between the measured profile and the target one，and evaluate the grinding quality directly and accurately.