With the deepening interaction between information network and physical network in power system, the reliability of modern power physical system and cyber system is inseparable. This paper based on IEC 61850 standard, it establishes a cyber-physical framework for distribution network. And the influence of cyber layer components on physical components is analyzed. This paper calculates the probability of different physical layer fault scenarios in the process of fault clearing. And it quantifies the coupling effect of cyber layer on physical layer. Taking the feeder system of distribution network as an example, and this paper calculates its reliability. The result shows that the fault of cyber layer components will expand the fault range of physical layer. And the switch communication link has the most significant influence on the distribution network.