Abstract: In order to solve the problem that the traditional suitability analysis of geomagnetic map only uses a single characteristic parameter as the evaluation index, which results in incomplete analysis results, a method of the suitability analysis of geomagnetic map based on fuzzy decision theory is proposed. Firstly, five main characteristic parameters, such as geomagnetic standard deviation, roughness, correlation coefficient, slope standard deviation and geomagnetic information entropy, are used as fuzzy indexes for weighted analysis, and the comprehensive evaluation value is obtained to evaluate the suitability of candidate areas. Then, based on the unscented Kalman filtering algorithm of geomagnetic anomaly, the earth magnetic anomaly grid 2 (EMAG2) model of part of the south China sea is selected as the geomagnetic anomaly reference map for the simulation experiment. The experimental results show that our proposed method has high reliability, and the comprehensive evaluation value can be used as a quantitative basis for the suitability analysis of geomagnetic map, and the optimal matching position can be obtained.