The invention relates to a comprehensive criterion type boundary protection method and system for a multi-terminal direct current power grid. The method comprises the following steps: obtaining current at a protection device installation position of a calibration circuit in a multi-terminal direct current power grid, and carrying out multi-layer wavelet decomposition on the current to obtain a plurality of frequency bands; obtaining an index for indicating the in-area fault sensitivity and the off-area fault reliability of the calibration circuit by using historical data, selecting a calibrated number of frequency bands from the plurality of frequency bands as characteristic frequency bands according to the index, and assigning the weights of the characteristic frequency bands; and determining the credibility of the characteristic frequency bands, updating the weights according to the credibility, determining an in-area fault or an off-area fault of the calibration circuit according to the updated weights, and performing corresponding protection on the calibration circuit. According to the technical scheme, reliability and sensitivity can be considered during boundary protection.