Voltage collapse is becoming a great threat to secure and reliable operation of power systems. Considering the impact of active power transfer on voltage instability， this paper proposes a coordinated control scheme based on model predictive control theory. First， an explicit criterion for stability margin is established based on the relationship between dynamic reactive power reserve and stability margin. Then， a sequence of control inputs consisting of generator's automatic voltage regulator（AVR） references and automatic generation control（AGC） references are determined in receding horizon manner to maintain system voltage profile and stability margin during load pick up and transient periods. Case studies are performed on New England 10 generator 39 bus system to demonstrate the method and validate the effectiveness of the proposed scheme. As an auxiliary function of AGC， the participation in voltage control is expected only when the system is approaching the verge of instability， therefore， both economic distribution and ordinary frequency control are preserved.