The invention provides an enumeration-method-based expected-energy-not-supplied (EENS) equivalence calculation method. According to the method, an external network and an internal network are distinguished according to a power grid topological structure, node sets of the internal network, the external network, and a boundary are divided, and power equipment parameters of all nodes in all node sets are obtained; an external network equivalent network is constructed, an equivalent parameter of the external network equivalent network is calculated based on the power equipment parameters, and a topological analysis model including the equivalent network is established; the topological analysis model including the equivalent network is combined with a preset constraint condition and thus an internal network minimum load shedding model with the consistent equivalent trend and sensitivity is constructed; and a reliability evaluation parameter is inputted, enumeration of all node element faults of the internal network is carried out successively and system state sampling calculation is carried out, and an expected-energy-not-supplied value is calculated. According to the invention, while an equivalent model is established, the consistency of the trend and the sensitivity before and after the equivalence is considered fully, thereby guaranteeing the calculation precision of the minimum load shedding and the system analysis effectively and improving accuracy of reliability evaluation.