The filtering performance of a Phase-Lock Loop (PLL) is insufficient because of the saturation suppression of PI controller. Thus a single-phase PLL based on an improved loop filter is proposed. The PLL improves the loop filter and the filter performance by adding an anti-saturation PI controller. Where the input contains both DC and harmonic interference, the phase-locking precision can be clearly improved by tracking the real-time phase of the power grid. Matlab/Simulink platform is used to simulate and analyze the adaptability and anti-interference of the improved single-phase PLL when the power grid is distorted. Experimental verification is conducted based on the experimental platform with the TMS320F28335 DSP development board as the core. The results show that this method can quickly and accurately track the frequency change of the system and achieve the phase-locking effect. This work is supported by the Natural Science Foundation of the Xinjiang Uygur Autonomous Region (No. 2020D01C068).