This paper uses Cassie arc model to simulate the common resistance, inductance series parallel circuit and rectifier circuit in normal operation and fault, and obtains the current data of different circuits and different states. In the linear load circuit, the arc fault current has obvious zero break characteristic, but the nonlinear load circuit does not have this characteristic. The fast Fourier algorithm is used to analyze the current harmonic variation in different states. The K-means clustering algorithm is used to establish the arc fault detection model, and the odd higher harmonic component of the current is taken as the eigenvalue into the algorithm. The model is tested by 70 groups of data, and the test results show the effectiveness of the model.