An interphase fault location method based on random forest algorithm is proposed targeting the impact of distribution line parameter errors on the results of interphase fault distance measurement. Firstly, four fundamental double-side fault location algorithms are selected, and the relationship among parameter error, measurement error, and ranging results is analyzed. The result show that it is difficult to describe the relationship by a linear and analytical expression. Secondly, a random forest model is established, and a nonlinear model is constructed with basic algorithm ranging results as input and precise fault location as output to describe the non-linear relationship among parameter error, measurement error, and ranging results. Therefore interphase fault distance measurement is completed. Finally, the digital simulation results show that the proposed model has high location accuracy and is not affected by parameter errors, fault location, initial fault angle and other factors. Also, the model is suitable for distribution network with high penetration distributed generation and has generalization ability and practical value has practical value.