Abstract: Because of the characteristics of its topographic distribution，it is hard for China to set up a Grid-based ionospheric correction model. In order to obtain accurate regional ionospheric correction，the wide area ionospheric correction triangular partition method is proposed. A triangular partition of the ionospheric delay model for mid-latitude in China was established using five ionosphere reference stations of the China seismo-ionospheric groundbase monitoring network. The precision of the method was examined by eight reference stations，the results show that，in the case of the existing network layout for the triangular partition of the internal area，ionospheric delay error can be improved to 90%;For the external triangular partition，hundreds of kilometers from the area，this method can also achieve correction accuracy of more than 80%.At the same time，GNSS data from four IUS tracking stations in United States and Canada were used to test this method. The results also verify the feasibility of this method，with important reference value to the wide area single-frequency ionospheric delay error correction.