Abstract: Aiming at the problem of long baseline initialization time and unstable positioning results in conventional real-time dynamic (RTK) positioning technology, a BDS/GPS wide lane Kalman filter RTK positioning method based on partial ambiguity fixing strategy is proposed, which can make full use of the advantages of long observation wavelength and easy fixing ambiguity of wide lane, and avoid the influence of low altitude angle satellite on ambiguity resolution. At the same time, Kalman filter method with additional wide lane ambiguity parameters is used to calculate floating-point solution to fix the position of satellites higher than the cut-off altitude angle of ambiguity solution, and to calculate the mid-long baseline of 25-76 km with intense ionospheric activity. Through three groups of experiments, the results show that: BDS/GPS dual system locates wide lane ambiguity jointly. The degree fixing rate is close to 100%, the baseline ambiguity fixing rate of 76 km is 99.9%, and the positioning accuracy is centimeter or quasi-centimeter.