Power distribution systems are conventionally designed as radial systems fed from a main source. However, when a distributed generation (DG) unit is connected to the system, the network is no longer radial. The presence of DG may affect existing protective relaying, especially overcurrent relays although DG has significant economic and environmental benefits. This paper proposed a novel protection strategy for coordinating the protection relays in power distribution system with high penetration of DG units. The proposed strategy coordinates the open/close states of the overcurrent relays by using the backtracking algorithm to determine the downstream and upstream paths leading to DG units. Initially, the faulty line is identified and the main protection algorithm determines the open/close states of relays so as to isolate the faulty line. In addition, a backup protection algorithm is considered to complete the protection coordination scheme in case of malfunction relays. Several case studies are considered to verify the accuracy of the proposed protection coordination method. The results verified that the proposed protection strategy is able to accurately coordinate the relays in a power distribution system with DG units.