Abstract: For the nonlinear system Kalman filter in surveying field, this paper proposes a new linearization method, after the analysis of two common linearization methods. By this method, the error of linearization is similar to extended Kalman filter. Furthermore, the linear observation equation is the same to the least square method, so the comparison between Kalman filter and least square can be done during the data processing, which is helpful to the precision analysis and quality control of the positioning. Especially for GPS positioning, the linear filter equations are listed.