The invention provides a method for determining stability of static voltage when regional power grid reactive power support capability is taken into consideration. The method includes the steps of modifying node types of a generator, commissioning a reactive power compensator and searching voltage weak nodes, setting a load model as a constant power model, setting stable calculating program simulation parameters, outputting V-T curve and P-T curve of the weak nodes, and determining the stability of static voltage. The load level is adjusted when the reactive power compensator is commissioned, and weak nodes are obtained according to the voltage change of various stations. The time for searching weak nodes is shortened, load station reactive compensation in discrete distribution is taken into consideration during a calculating process, and the calculating result obtained meets the operation situation of a real power grid. The problem that convergence near voltage stability critical point for common trend calculating method is not easy can be solved, the efficiency for calculating limit of a large power grid is improved, and the limiting value obtained is more accurate. The load increasing time and gradient for specific region can be controlled. The method is wide in application scope.