Abstract: In allusion to the practical problems for preventive control,an on-line preventive control algorithm for static voltage stability in large-scale power system was presented.The generation power distribution factor for coming future was introduced as control parameters for static voltage stability margin,based on sensitivity information of loading margin with respect to control parameters,the centralize scheduling strategy and the candidate control group strategy were used to establish a linear programming model for preventive control,and then the control scheme to avoid voltage instability was given.The feature of this algorithm is that serious contingencies and unstable contingencies can be solved in the same mathematical model;The adjusted amount of other control parameters will be reduced through the application of generation power distribution factors in the future.Tests with a practical 750-bus power system indicate that the proposed method is effective and applicable.