Marine state information is important in many areas of research, e.g. marine monitoring, marine weather forecast and climate forewarning, and this information can be collected by ocean buoys. In the process of measurement, Doppler passive positioning is used to determine the position of the buoy. This paper aims to identify the factors that influence the buoy positioning accuracy. It is derived from the error formula that the positioning accuracy of the buoy is related to the relative position error between satellite and buoy, satellite orbit error, and frequency measurement error. In the simulation, satellite ephemeris data are generated, the iterative location algorithm is used to get the location of buoy, and noises are analyzed at last. We find that the relative position and frequency measurement error have a significant impact on the positioning accuracy of the buoy. Therefore, in order to improve the buoy positioning accuracy, it is necessary to select a satellite position that is near the radiation source but not directly above it. Improving the frequency measurement accuracy will also greatly enhance the positioning accuracy.