For users of satellite navigation and positioning, ionospheric delay error is one of the main error sources that affect the accuracy of navigation and positioning. Dual frequency users can eliminate the influence of ionospheric delay according to the combination of double frequency observations. For single frequency users, ionospheric delay correction is needed according to the ionospheric prediction model of system broadcast. During the solar storm,the geomagnetic field will produce a certain degree of disturbance and the ionospheric electron concentration will change. On September 6, 2017,the solar flares of class X9.3 and the solar flares of class X8.2 again broke out on September 10, 2017. The ionospheric electron concentration changed obviously during this period, which affected the positioning accuracy of Beidou single frequency users. In this paper,the ionospheric changes before and after the solar storm, the availability of Beidou satellite and the difference of pseudo-range positioning results under different positioning modes are studied and analyzed by using the measured data of BDS from Beijing, Sanya and Chengdu.