Voltage security is an important concern in power networks as a result of system heavy loading. In this paper, a new CONTINUATION METHOD is presented. which has three outstanding features for voltage security assessment. In this CONTINUATION METHOD, adaptive step size is applied. For adaptation, a criterion, based on rate of voltage drop, is used. This METHOD can monitor the voltage security status of power systems under various topologies, load levels and generation patterns. Different load and generation scenarios can be analyzed by this METHOD. Also, the proposed CONTINUATION METHOD uses local analysis for evaluation of power system voltage stability after contingency or pre ntive action. The proposed METHOD has been examined on the test system of the New Zealand and Iran's power network. Obtained results confirm the validity of the developed approach. Also, the most vulnerable buses of these test systems have been sorted by a new ranking function. A discussion about this ranking function and its results has been presented.