The invention belongs to the field of energy chemical industries, and particularly relates to a method for enhancing water-electrolyzing hydrogen production performance of a copper sheet through hydrothermal treatment on the surface of the copper sheet. The method comprises the steps that firstly, the copper sheet is subjected to ultrasonic cleaning in acetone, deionized water and absolute ethyl alcohol so as to remove oil stains on the surface of the copper sheet, then the copper sheet is subjected to 160 DEG C hydrothermal treatment in a KHCO3 aqueous solution with the 2% mass fraction for 10 hours so as to change the structure and morphology of the surface of the copper sheet, and when the copper sheet is used as an electrode for water-electrolyzing hydrogen production, the copper sheetsubjected to hydrothermal treatment shows the characteristics of being low in initial potential and high in hydrogen evolution efficiency. The method has the main characteristics that surface modification of the copper sheet is achieved by using the simple, convenient, environment-friendly and nontoxic method, the performance for water-electrolyzing hydrogen production of the copper sheet used asthe electrode is greatly improved, and it is expected to realize large-scale low-cost water-electrolyzing hydrogen production.