The invention discloses a method and a device for power station condensed water fine treatment. After condensed water enters a pipeline, the sequence of the condensed water flowing through filter equipment (1) and ion exchange equipment (2) is adjusted through controlling valves arranged in the pipeline to satisfy the requirements of a condensed water fine treatment system under operation conditions at different stages. The invention has the advantages that the equipment is simplified, the area occupied by the equipment is saved, the high requirement on water quality of large-flow and high-parameter unit is satisfied, the water required by the unit for startup is greatly saved, the unit can be put into operation rapidly, the system manufacturing cost is reduced and the quality of the produced water is improved.