The invention discloses a fault diagnosis method of a switching current circuit. The fault diagnosis method comprises the steps of: first, carrying out sensitivity analysis on components of the switching current circuit, setting the fault types and collecting fault information; then, carrying out pre-processing on the acquired information to acquire a dimensionality reduction characteristic vector and a cloud model digital characteristic value; optimizing a wavelet neural network structure weight value and a threshold value by adopting a fish swarm algorithm; and finally, carrying out diagnostic analysis on parameter data to acquire the fault type. Through adopting the fault diagnosis method, the mode of data processing is more reasonable, the network structure is more stable, the diagnosis accuracy is higher, and the convergence rate is higher.