It is very important for single frequency network to realize high precision clock synchronization in Iot module connected to power system by power line carrier.However, the traditional clock synchronization method is not suitable for clock synchronization under power line carrier because of its low synchronization accuracy. In order to solve this problem, the hardware and software are studied. On the hardware, the high precision clock adjustment of physical layer is realized by using fractional phase-locked loop with high resolution output frequency.Software on the application of fuzzy control theory, the clock synchronization algorithm based on interval, to collect and analyze each receives the timestamp, reasonable adjust clock variables, study score type phase-locked loop to equipment clock frequency adjustment rules, to calculate the optimal clock adjustment parameters, realized the fast STA clock and CCO clock synchronization,keep the clock stable and keep the clock error within, significantly improve the clock accuracy, the accuracy and stability requirements of the Iot clock are fully met.At the same time, such high-precision synchronous clock provides technical guarantee for the application of Iot module in single-frequency network.