In order to accurately describe the impact of dynamic regulation of generators on critical points of static voltage stability and keep generators operate in the safe zone， a new generator model is constructed by nonlinear complementarily constraints and a nonlinear programming model for voltage stability critical point considering generator capability limits is proposed. The type of critical point is judged through analyzing the strict conditions of complementarily constraints of generator field induced voltage， stator current and terminal voltage. The numerical results of five IEEE test systems indicate that the proposed model can describe the dynamic characteristics of generators and calculate the voltage stability critical point more accurately， the exact judgment of the critical point type and the key generators could be achieved.