The main functions and features of Fujian on-line voltage stability monitoring and control（VSMC） system are presented in this paper. Within the scan period of energy management system（EMS）， the load margins of current operation state and a set of credible contingencies are computed at a group of predefined load directions. Once the unstable or severe contingencies are identified， the voltage stability control（VSC） module is activated to produce the preventive control actions. At the same time the new voltage limits of all pivot buses are given to automatic voltage control（AVC） system. A sensitivity and successive linear programming technique based control algorithm is used in VSC module to obtain the optimal control solution and coordinate the voltage stability control with the static security corrective control. The salient feature of Fujian VSMC system is that the on-line voltage stability close-loop control is realized partly by interfacing with the existing AVC system. The operation results of Fujian VSMC system show that it can effectively help operators to monitor the voltage stability situation and take actions to increase the voltage stability margins automatically.