Abstract: The vibration of the charging belt is reduced by adjusting the belt's tension while an electrostatic accelerator is running. The paper presents a simple calculation model to derive the basic law of the vibration of the charging belt. The results show that the tension is relevant to the belt's charge and velocity, and exist an optimal relation between the belt's tension and velocity by which the vibration will be reduced to the least. Calculation is carried out and applied to the faci lity. The effects are rather good.