Abstract: Because the deviation between predicted and practical load level is not considered in the existing voltage control scheme, voltage control effect cannot be guaranteed. So after introducing load fuzzy number to describe the load deviation uncertainty, an optimal coordinated control method for long-term voltage stability is proposed by considering load fuzziness. Based on the quasi-steady-state control model, in which minimum voltage deviations for load bus and control cost are regarded as objective, and continuous and discrete time differential-algebraic equations are taken as constraints, a fuzzy nonlinear programming model for coordinating voltage control is built. Then according to the maximum membership principle, the fuzzy nonlinear programming issue is converted into a common nonlinear programming problem which is solved by interior-point method. The effectiveness and robustness of proposed method are verified through the New England 10-machine 39-bus system.