In order to improve the efficiency of substation electromagnetic environment information collection and the accuracy of data measurement, an intelligent mobile monitoring device is designed and manufactured. The device includes unmanned platform and electromagnetic environment monitoring module. Self-designed power frequency electric field probe can realize synchronous measurement of power frequency electric field in three directions. The power frequency magnetic field acquisition circuit with reset circuit can eliminate the abnormal problem when the magneto-resistive sensor is in the strong magnetic field interference. External temperature and humidity module ensure measurement accuracy. External temperature and humidity module are installed to ensure the accuracy of measurement and measurement. The electromagnetic environment is measured in the actual 110kV substation with this device, which can walk and measure independently according to the specified path accurately. A three-dimensional model is established to simulate the spatial electromagnetic field distribution. The comparison between the measured data and the simulation data shows that they have the same trend, and the average error is less than 5%. Considering the simplification of simulation model, the error is acceptable. The accuracy of the measurement results is verified.