First，the working principle of SIEMENS phase-locked loop （PLL） is analyzed，then the equivalent conversion of FIR filter and inverse tangent segment is conducted，and the analysis of the frequency tracker is carried out，and the discrete domain mathematical model of the phase-locked loop is established. Next，the transfer function of the PLL is analyzed from three aspects of stability，dynamic response and steady-state error，and the restricted range of each parameter of the PLL system is obtained. Then，the new and old phase locked loops are tested under the interference conditions of frequency jump，frequency slope change，phase jump and harmonic intrusion，and the new parameters are found to have better phase locked performance. Finally，phase-locked loops of the old and new parameters are simulated and compared in the CIGRE HVDC benchmark model and Guizhou—Guangdong Ⅱ project model. The results show that the new parameter PLL can suppress the subsequent commutation failure more effectively under the AC faults，and improve the fault recovery performance of HVDC transmission system.