Estimation for the level of extreme geoelectric field can provide a basis to quantify the risk of the grounding technology systems due to magnetic storms. The extreme value model of geoelectric field is presented on the basis of the EVT. Firstly, the years maximum sample data of geoelectric field are constructed by using the geomagnetic data, and the general Pareto distribution model is established. Secondly, the model is examined by the mean residual life plot and the Q-Q plot, and the parameters are estimated by Bayes method. Finally, the return period *i.e.*, geoelectric field extreme value, was calculated. The 52 years' data of geomagnetic storms and the Earth resistivity model of Shache, Xinjiang are used to estimate the geoelectric field. The geoelectric field of 50-year is 3.288V·km^{-1} and that of once-in-a-century is up to 3.332V·km^{-1} in mid- and low-latitude area. By contrasting with the existing literature analysis, the credibility of model is validated.