We propose a novel method for characterizing the oxide traps that participate in random telegraph noise (RTN) by using charging history effects on the traps. In this method, the variation in the frequency of the high/low drain current derived from RTN with the charging history is monitored instead of the time-scale parameters that are usually used. Moreover, we also propose a method to determine the number and charging conditions of the traps. These methods are particularly effective for characterizing individual oxide traps in multi-trap RTN.