Secondary Voltage Control is a new way of voltage control,firstly the power system is divided into many control areas whose electric distance is remote.The partitioning method of secondary voltage control is studied and an algorithm that combination of the threshold search and dynamic scatter is presented.That is,the initial grouping scheme is obtained by searching the threshold value.The dynamic scatter method then is used to regulate and improve the initial results.The method is based on system's physical character,it's unnecessary to modify the network's model and analysis the eigenvalue,so the compute rate is fast.Through comparing the method and the traditional methods,this method is proved to be a reasonable and feasible partitioning scheme.