This paper presents a new algorithm of identifying the different modes of ferroresonance (FR) using voltage signals. The voltage signals are simulated from a ferroresonance model that represents a voltage transformer energized through a grading capacitance of opened circuit breakers. Different modes of ferroresonance voltage signals were obtained by simulating various value of grading capacitance, system voltage and interrupting time. The mode's identification is automatically determined by correlating the sustained period of different ferroresonance mode signal and the sustained period of tested voltage signal. Detecting the types of ferroresonant modes plays an important role as a pre-testing tool or diagnostic tool to identify the range of parameters that would lead to the fundamental frequency ferroresonance phenomenon. The simulation is carried out by using Matlab.