The invention provides an inverter power fault detection method and system. The method comprises the following steps: collecting DC bus voltage, input power and output power of an inverter; determining a power partition located by the input power of the inverter; performing normalization on the DC bus voltage, and performing normalization processing on the input power of the inverter according thepower partition located by the input power of the inverter; obtaining a power loss value according to the normalized DC bus voltage and the input power of the inverter and the power partition locatedby the input power; and determining the power fault according to the output power of the inverter and the power loss value. The accuracy of the fault judgment is improved.