The modern power system networks are being executed under stressed conditions due to continuous increase in power demand. The voltage collapse can appear quite precipitously. So we need uninterrupted control of the system state. This paper compares the performance of several indices which furnish important information about the proximity of the system to voltage collapse. All these method has been implemented on IEEE 39 bus test systems, where their performances of these indicator is explored over both stable and unstable region, by varying the load at a particular bus and gradually increasing the load in all load buses.