Ionospheric delay is one of the main errors in GNSS positioning. The ionospheric total electron content (TEC) is the key information reflecting the ionospheric delay. Generally dual-frequency pseudo-range observations smoothing by carrier phase are used to extract TEC, resulting in observations including ionospheric delay, differential code bias (DCB) of satellites and receivers. This method ignores the known high-precision information of satellite position and clock, and the accuracy is limited by smoothing process. This paper, based on the raw observation data, performs uncombined PPP on the base station, separates the DCBs, extracts the TEC information of each station, establishes the regional ionospheric delay model, and finally verifies the ionospheric model accuracy by using single frequency PPP. The experimental results show that the model accuracy is better than 3TECU, and the single-frequency PPP accuracy is better than 0.3m.