The paper includes that the increasing amount of distributed generation (DG) in power system will deeply affect the network structure, the direction and amperage of short-current in the system，and will affect the reliability and stability of the net. Taking the 10kV network as an example, the paper explores the effect of DG on protective device such as 3-sectional current protection based on circuit breakers, fuse-fuse coordination and reclosure. It concludes that if protection scheme is not changed, the best way to maintain coordination in presence of arbitrary DG penetration is to divide the network into several zones, then disconnect the right DG selectively and instantaneously in case of fault.