Power systems can get larger benefit when thermal units， nuclear units and wind parks operate with pumped-storage stations. A method for quantitative evaluation of the emergency benefit in the pumped-storage station is presented based on the analysis of failure modes， in which the detailed reflection process of all kind of units is simulated in the case of system faults. Using the equifinal substitution method evaluates the fault spinning reserve benefit， and the annual expected energy not supplied， the sum of coal consuming， waste emission and reliability are regarded as evaluating indices. The total calculation model established contains three sub-models as follows: load model， generation model and increasing power output model. The problem that the reasonable division between load leveling capacity and fault reserve capacity of a pumped-storage station is discussed. The case study of an actual pumped-storage station shows the practicability and feasibility of the method.