At present, the power electronic converters with its superior performance have been widely used in petroleum, coal seam gas and other industrial and mining production site. Pre-charge circuit is an important link which must be considered in the design of frequency converter. Pre-charge circuit which has high performance can not only improve the safety and reliability of frequency converter, but can also extend the service life of the device and save the maintenance cost. In view of the shortcomings of the traditional pre-charge circuit, this paper designed two news types of pre-charging circuits which were special used in the frequency converter, and carried on research on the performance of the circuit through the MATLAB Simulink, compared and analyzed of the advantages and disadvantages of various pre-charging circuits, which were a certain guiding significance to the design of frequency converter.