Abstract: The emerging services in smart park are carried out with data support provided by power internet of things (PIoT) devices, and these services have strict time synchronization requirements. How to achieve power line carrier (PLC)-based high-accuracy and reliable synchronization has become a key issue. First, this paper establishes a PLC-based accurate time synchronization network mode, and calculates the synchronization error based on the improved precision time protocol (PTP). On this basis, a digital phase-locked loop-based frequency offset compensation model is established to reduce the cumulative error. Then, the time synchronization error minimization problem of station (STA) is proposed. Finally, an empirical matching-based accurate time synchronization algorithm for PIoT is proposed, which optimizes the time synchronization route selection of STA by adjusting the synchronization matching costs. Simulation results show that the proposed method can effectively improve the time synchronization accuracy.