Abstract: This paper proposes a time synchronization scheme for local communication in the perception layer of power Internet of things. The scheme does not need to broadcast beacon frame with time stamp for synchronization. Instead, it utilizes data acknowledgment frame of MAC layer, and only when there is no data transmission in a whole synchronization period, it unicasts the specified packet for synchronization which greatly reduces synchronization overhead. Data acknowledgment frame does not need channel access which reduces the impact of random channel access delay and ensures synchronization accuracy. Simulation results show that synchronization accuracy can reach tens of microseconds when the linear regression algorithm with 8 historical values is adopted, which can meet the time synchronization accuracy requirements of applications in power Internet of things.