The invention provides an electric coach air conditioning system and a frequency converter of the electric coach air conditioning system. The electric coach air conditioning system comprises a dynamical power source, a low-voltage control power source, the frequency converter, a compressor, an evaporation draught fan, a condensation draught fan and an air conditioning control panel. The air conditioning control panel is electrically connected with the low-voltage control power source and the frequency converter, the frequency converter is electrically connected with the dynamical power source,a low-voltage control power source and the compressor, the evaporation draught fan and the condensation draught fan are electrically connected with the frequency converter and the dynamical power source, or the evaporation draught fan and the condensation draught fan are electrically connected with the frequency converter and the low-voltage control power source, the frequency converter comprisesa control unit, the control unit comprises a microprocessor, and the microprocessor receives an operation parameter command of the electric coach air conditioning system, acquires state parameters ofthe electric coach air conditioning system and outputs a control command of the electric coach air conditioning system.