Abstract：On the basis of a new model joining the IGRF model with the observation data of Chinese geomagnetic stations to build a magnetic field model throughout China is builtup,which simplified the calculation of the second order ionosphere effects.In this paper the results calculated by the new model is compared with the real data and it is given that the residual error is in 2.5 millimeter in the fixed number of year. The secondorder ionospheric correction for positioning calculated with the new model is basically the same as with the IGRF model. The model proposed in this paper can not only guarantee the accuracy,but also make the calculation of the secondorder ionospheric effects simplified and improve the computing speed.
