Introduces the development status of Beidou satellite navigation system and the working principle of Beidou satellite-based augmentation system. The main sources that affect the positioning accuracy of satellite navigation were studied,which can be divided into the following three categories:errors related to satellite clock, errors related to apostrophe delay, and errors related to ionospheric delay. After this,the ionospheric delay that is the most important source of error affecting positioning accuracy is analyzed. Aiming at the ionospheric error, an optimization algorithm for the grid ionospheric model is proposed, and a better optimization model is obtained through data acquisition and algorithm simulation comparison. The comparison of simulation results proves that the optimized algorithm can effectively reduce the ionospheric error value.