The invention provides a method for evaluating the reliability of a power system accessing new energy and relates to the technical field of power grids, and the reliability of the power system that accesses the new energy can be reasonably evaluated. The method includes a step of establishing uncertainty models for each piece of conventional equipment, a load, and new energy in a power system, a step of sampling the states of each piece of conventional equipment, the load and the new energy, a step of establishing a load-shedding optimization model of the power system and carrying out fault state judgment with a minimum load-shedding quantity as an optimization target to obtain a minimum load-shedding quantity of the power system in a current sampling state, a step of counting a load-shedding probability and a load-shedding expected value of the power system in the current sampling state, and a step of calculating a convergence index of a target function of the load-shedding optimization model and judging whether the convergence index satisfies a set requirement or not, ending sampling if so, evaluating the reliability of the power system with the load shedding probability and theload shedding expected value as reliability evaluation indexes, and sampling again if not.