The techniques of distribution system voltage control,such as on-load tap changer (OLTC),step voltage regulator (SVR),switched capacitor bank (SCB),smart inverter,etc.,work in distribution system to maintain the voltage profile. Due to the increasing penetration of photovoltaic (PV) and its intermittent nature,the voltage fluctuation in distribution system becomes more severe and even arise the voltage violation if the controls of them are not coordinated well. The smart inverter with flexible reactive power control plays an important role to mitigate the voltage variation,but the settings of the volt-var control curve of each one which distributed in the feeder will determine the coordination of the voltage control. The tap changed times of SVR,switched times of SCB,and bus voltage variations can be improved if each control curve of PV smart inverters are set properly. In this paper,the settings of volt-var control curve will be optimized and analyzed by gravitational search algorithm,and the outcomes will be a good suggestion for distribution system operators to formulate the voltage control strategy.