The invention discloses a surface treatment method for water-corrosion-resistant refractory metal molybdenum. The method includes the steps that molybdenum powder is prepared, press forming is carriedout, sintering is carried out, heat machining and heat treatment are carried out, an experimental sample is prepared, and ion irradiation is carried out. The vacuum degree in a sample irradiation cavity is kept, Ar ions are adopted for irradiating the surface of the sample at a set temperature, the dosage is selected at 3-4*1016 ion / cm<2>, the acceleration voltage is selected at 350-400 KeV, theaverage atom displacement energy is selected at 25-35 eV, and a molybdenum block obtained after surface treatment is obtained. The corrosion resistance of the sample obtained before and after irradiation is evaluated through electrochemical open circuit potential, a polarization curve, impedance and other tests. The refractory metal molybdenum treated with the method has good corrosion resistance,and the burn-out life of the molybdenum in a water medium is greatly prolonged. By researching and analyzing the influences of the neutron irradiation effect on corrosion, scientific data are provided for application of the molybdenum and alloys thereof in the nuclear power field.