The invention relates to a method for preparing flax fiber by a combined process of a candida tropicalis DK2 strain and hydrogen peroxide. The method comprises the following steps: (1) culturing the strain; (2) preparing a crude enzyme solution; and (3) mixing a flax raw material after sterilization and a mixed solution of the crude enzyme solution and hydrogen peroxide according to the mass-to-volume ratio of 1: (10-30), regulating a pH value, then putting into a shaking bed for treatment, finally adding sodium hydroxide, increasing the temperature, degumming, removing a degumming solution, washing, stopping washing when the pH value is natural, and completing degumming. The strain adopted by the invention is short in growth period, the strain is less liable to pollution, the treatment cost is low, and the degumming condition is mild; and the degumming method is simple in process flow, the time is shortened, the energy consumption is reduced, the pollution emission is reduced, and the method is conductive to environmental protection.