The procedure of cavity BPM resolution analysis was summarized. We applied various types of correction functions, such as the simplest linear model, linear combination of all variables, and additional 2nd and 3rd order terms. A least-square method using a multiple regression analysis was used to determine coeffcients in the correction function. The resolution was estimated to be 24.4 nm with the linear model, and it improved to be 16.3 nm with higher order terms.