The invention discloses a one-step hydrothermal manufacturing method of a dye sensitization solar cell FeSe2/Fe counter electrode. The method comprises the following steps that an iron sheet is processed by alkali and acid so as to remove a surface oil contaminant and oxide, the iron sheet is cleaned and then is placed in a stainless steel reaction vessel with a polytetrafluoroethylene lining at a certain angle; besides, hydrazine hydrate with a 0.21mol/L-4.2mol/L molar concentration and a selenium powder with 0.01mol/L -0.8mol/L molar concentration are dissolved in deionized water and are fully mixed, and then a mixture is transferred to the reaction vessel; at 120DEG C-200DEG C and for 2-18 hs, complete reaction is performed, a sample is taken out, cleaned and dried in a vacuum state, and then the counter electrode is acquired. The manufacturing method of the FeSe2/Fe counter electrode is simple, cost is low, a manufacturing period is short and rapid and large-scale manufacturing can be performed.