A method based on controlling UEP method to analysis the power system voltage stability is proposed. The heuristic method is employed to get the initial value of controlling UEP which is related to power system’s voltage stability in the first step. Then a Newton homotopy method is introduced in order to reduce the sensitivity of dominant unstable equilibrium point to initial values, which means that the proposed initial value can converge to the dominant unstable equilibrium point effectively. In addition, the dynamic load model of multiple motors is considered, and the dominant load bus is found by identifying the weak voltage node under large disturbance, which improves the applicability and extensibility of the heuristic method. Combined with the energy function and the controlling UEP, the critical clearing time of transient voltage stability of multi-machine system can be obtained with an acceptable engineering accuracy. Finally, the feasibility and effectiveness of the proposed method is illustrated on the three-machine nine-bus system.