The invention relates to a middle-high-voltage power cable residual life evaluation method considering stress randomness. The method comprises the steps of determining thermal stress of a power cable considering the randomness, obtaining the stress of the power cable considering the randomness, and evaluating the residual life of the power cable based on a random model. According to the step of determining the thermal stress of the power cable considering the randomness, the thermal stress of the cable within step-size time of each stair is obtained; according to the step of obtaining the stress of the power cable considering the randomness, an electric field intensity curve, changing in a stair shape, of the power cable is obtained; according to the step of evaluating the residual life of the power cable based on the random model, a cable service life model and a cable electric heat degeneration amount random model of the power cable under the synergistic effect of electric stress and the thermal stress are obtained, and a mathematical expectation value and a variance of power cable service life degeneration cumulant are estimated. The method improves the accuracy of middle-high-voltage power cable residual life evaluation and achieves the technical effects of determining the cable residual life in cable asset management and accurately formulating a scientific replacing scheme.