Nowadays, the dual-frequency GNSS magnitude has been widely used to build up the ionosphereic vertical model and become an important tool for studying global or regional ionosphereic disturbances. The study aims at the newly built Continuous Operational Reference System of Taichung city as objects, build up the city ionosphereic model in Taichung area based on the CORS system. Last, perform the single-frequency point positioning test with the ionosphereic model, and the average accuracy increases to 50% to 60%. While within the short 2 hours, performing the single point positioning may reach the best accuracy to 95%.