Multi-stage adhoc power line communication is an important transmission scheme for operation control instructions and information acquisition data in the low-voltage distribution network. The realization of accurate time synchronization between acquisition equipment based on PLC is of great significance to improve the quality of network operation and customer service lean level. Given the processing delay of timing protocol, accumulated delay caused by multistage relay, this paper proposes to estimate the transmission delay by extending the data domain of beacon frame in media layer protocol and introduce the downlink timing confirmation frame in a hierarchical manner. As a result, the timing offset caused by protocol processing and sampling time deviation is reduced. Through simulation results, the synchronization accuracy of the proposed clock synchronization method can reach 30 μs level, which is better than that of the traditional method at ms level.