The invention provides a method and a system for evaluating a time domain index of a corona current signal. According to the method and the system, after a time domain index is set, a time domain index value is calculated for the corona current signals under different voltage grades of actual measurement; an index vector value is generated after normalization is carried out; then, a F-score formula is used for carrying out significance analysis on the time domain index according to a vector value of the time domain index; rational analysis is carried out through a variance devoting rate; screening of independence of the time domain index is carried out through calculation of a correlation coefficient and in combination with a F-score formula calculation result; and the index passing through rational analysis and independence screening is subjected to effectiveness analysis of classification of the time domain index by using a support vector machine. According to the method and the system, a uniform time domain index is set for the corona current signal under the power transmission line; the time domain index of the corona current signal is evaluated from four aspects of significance, rationality, independence and effectiveness; and a theoretical foundation is laid for the research of the corona current of a subsequent extra-high voltage transmission line.