The distribution of power equipment in substation is concentrated and their shapes are complex. The whole distribution of power frequency electric field in substation is influenced by 500 kV switching field, transformers and reactors. Firstly, in order to simplify the calculation, 3D modeling of these large power equipment is carried out. Then Biosaval’s Law is applied to the calculation of power-frequency magnetic field, and then the distribution of power-frequency magnetic field around the large power equipment is calculated and analyzed. The results show that the power frequency magnetic fields in the 500 kV switching field area varies between 0.1 and 1.6 μT, the power frequency magnetic fields in the transformer area varies between 1 and 6 μT, and the power frequency magnetic fields in the reactor group varies between 0.1 and 4.5 mT, which is relatively large. The results can provide reference for optimizing the distribution of power frequency magnetic field in the design stage.