Provided is a cooling method for exhaust steam of a generator set. According to the cooling method for the exhaust steam of the generator set, demineralized water is continuously conveyed into a condenser in the operation process of a steam turbine set, after the demineralized water entering the condenser is atomized, the atomized demineralized water is sprayed to the throat portion of the condenser to enable heat exchange to be continuously conducted between the demineralized water and the exhaust steam of the generator set, and a cooling pipe of the condenser is assisted in cooling the exhaust steam of the generator set, and the vacuum degree of the condenser is improved; and meanwhile the demineralized water sprayed to the condenser and condensed water are pumped out through a water exhausting device so as to prevent the phenomenon that the water level of the condenser rises and then influences continuous spraying of the demineralized water into the condenser. The invention further provides a corresponding cooling device for the exhaust steam of the generator set. By the adoption of the cooling method and device for the exhaust steam of the generator set, the demineralized cooling water is atomized and then continuously sprayed into the condenser, heat exchange is made to be continuously conducted between the demineralized water and the exhaust steam of the generator set, and therefore the defect that the heat exchange ability of the cooling pipe of the condenser is insufficient is overcome; and the problem that the vacuum degree of the condenser is low is thoroughly solved, and the heat economical efficiency of the generator set is improved.