Distributed generation will be popular in the future. This paper placed great emphasis on the voltage stability of distribution networks with distributed generations. First of all, distributed generations were classified into four types, according to different network interface and operation. Every kind of node type was build mathematical model which used in the Newton-Raphson power flow algorithm. Secondly, the paper present a commonly used index used in the analysis of static voltage stability of distribution networks. It focused on the static voltage stability index which is based on the existence of power flow solution, and analyzed the relation between this index and load scale factor (LSF) by calculation of practical distribution network. Finally, the load flow algorithm with distributed generation was programmed. Through practical calculation example，it study on impacts of type, location, capacity and power factor of DG on static voltage stability of distribution networks and provides directions of the planning of distributed generations in distribution network.