The invention provides a method for evaluating operational safety of an interconnected power grid. The method includes computing various indexes of the power grid and a new project in each power grid sub-area to be used as original sample data, and constructing a sampling space; adopting the proportion of load of each power grid sub-area to total load of the power grid as an expert weight, obtaining a composite value of each single index by means of weighted computation and using the composite values as sample data; computing the correlation degrees of the various indexes, and obtaining objective weight of the various indexes by means of normalization computing; carrying out normalization based on the objective weights of the various indexes after composite values of the single indexes are computed, and computing correlation coefficients; carrying out weighted computation for the objective weights of the single indexes and the obtained correlation coefficients and obtaining the quality sequence of the power grid and the new project; and obtaining an overall safety index of each power grid sub-area by means of weighted computation according to the objective weights of the indexes, using the overall safety indexes as sample data, computing correlation degrees of each power grid sub-area by the aid of grey correlation analysis, and obtaining the quality sequence of safety of the various power grid sub-areas.