Vulnerability assessment in power systems is to determine a power system`s ability to continue to provide service in case of an unforeseen catastrophic contingency. It combines information on the level of system security as well as information on a wide range of scenarios, events and contingencies. To assess the level of system strength or weakness relative to the occurrence of an undesired event, a quantitative measure based on vulnerability index is often considered. In this study, a new vulnerability assessment method is proposed based on total power system loss which considers power generation loss due to generation outage, power line loss due to line outage, increase in total load and amount of load disconnected. The objective of this study is to investigate the effectiveness of the new proposed method in assessing the vulnerability of power system when subject to various contingencies. The performance of the proposed vulnerability assessment method is compared with other known vulnerability assessment methods based on anticipated loss of load as well as comprehensive system information of individual system components. In this study, vulnerability analysis was carried out on the IEEE 24 bus test system using the Power System Analysis and Toolbox (PSAT) and the vulnerability indices were calculated using the Matlab program. Obtained results, indicate the efficiency of proposed method.