A model of optimal power flow with UPFC and minimum voltage stability constraint is proposed. In the model, equivalent sources of series and shunt side UPFC are built so that amplitude and angle of such sources are treated as variables. Based on Benders decomposition, two sub-models are established. The previous one is OPF model, while the other is used to deal with minimum voltage stability constraint. The coordinated optimization between master and sub-models is established by Benders cut, and the solution of the whole model is finally realized. In the end, southern Suzhou power grid is applied to test the correctness of the above model.