Aiming at the problem of phase-locked loop (PLL) which can accurately obtain the voltage phase information of power network, when the frequency changed suddenly, the large phase deviation affected the phase tracking performance, in this paper the second-order generalized integrator (SOGI) was improved by introducing a proportional component, and proposed an improved digital phase detector structure based on the improved SOGI and Park Transform, and explained the working principle of PARK transform in detail, the control structure of the improved PLL was analyzed, then it is modeled and simulated in Simulink and realized digitally with FPGA. The simulation results show that the PLL composed of the improved Phase detector has better phase-locked performance, high phase-locked precision and fast time response compared with the traditional PLL.