In order to solve the problem of accurate measurement on the parameters of low-voltage power supply lines，in this paper an intelligent measurement method of low-voltage power supply line impedance based on phase-to-mode conversion is proposed. And the least-squares optimization model is established to optimize the impedance parameters to achieve accurate measurement. Finally，the practical example verifies that the method is effective and feasible. The method realizes the online identification of the impedance parameters of the low-voltage power supply line under different working conditions，and provides a basis for the evaluation of the operation state of the power supply line.