The invention relates to a power distribution network time synchronization system and method, and particularly relates to an intelligent power distribution network time synchronization system and method based on a PTN+EPON communication system. The intelligent power distribution network time synchronization system comprises an accurate clock source device. A primary clock port of the accurate clock source device is connected with a secondary clock port of a local end PTN device via an IEC61588 protocol. The primary clock port of the local end PTN device is cascaded with PTN devices in multiple transformer stations so that an annular structure is formed. The primary clock port of each PTN device in each transformer station is connected with a router which is connected with the secondary clock port of an OLT device via a switch. The OLT device is connected with an ONU device via an optical fiber. The primary clock port of the ONU device is connected with a power distribution terminal. According to the intelligent power distribution network time synchronization system, only a GPS is used as a clock source. An IEC61588 technology is applied, accurate time is transmitted step by step via a communication system so that time synchronization of the whole intelligent power distribution network is realized. Time accuracy is superior to 1 microsecond theoretically so that dependency on the GPS is low, and a requirement of the intelligent power distribution network towards time synchronization can be met. Therefore, the intelligent power distribution network time synchronization system is simple in structure and high in practicality.