Distributed Generation (DG) has a significant effect on the operation condition of the distribution network, especially on the voltage profile of distribution network and total power losses. This paper describes a detailed model designed for DGs and loads to reflect the exact condition of the power flow. Then a Volt/Var Control method based on rules is introduced. Next the IEEE 13 node feeder with DG and detailed load model is selected as the simulation example. Finally this method is applied to prove the validity of this method by the indicators such as voltage profile and total power losses, and to analyze the continuous effects of Volt/Var control of distribution network with DG.