The role of power information collection system in smart grid construction becoming more and more important, the accuracy and efficiency of the collection of power information is the key technology of building smart power utilization system. In order to improve the time accuracy of the power information collection system, this paper present an NTP time synchronization method based on asymmetric coefficient modification, using client/server mode and broadcast mode to synchronize the acquisition terminal and the meter of power information collection system from top to bottom respectively.Finaly, the time synchronization system of power information collection is studied, which effectively improves the accuracy and efficiency of power information collection system.