Based on slow dynamic characteristic, the components including generator, excitation current limiter, armature current limiter, transformer with on-load tap changer (OLTC), load and secondary voltage controller, which have great effect on long-term voltage stability, are modeled. Hence the quasi-steady-state model of a whole power system is constructed. A sequence of transient equilibrium points in dynamic evolution process are computed using time-domain simulation method, according to which dynamic process of long-term voltage stability can be depicted and its fast simulation can be realized. Also simulation results on a 10-machine 39-bus system are used to analyze effect of the secondary voltage controller on voltage stability. Results show that the secondary voltage controller can improve voltage profile of the controlled area and voltage stability during voltage drop or instability.