The invention discloses a method for preparing a hydrogen permeation preventing coating by aluminizing by adopting room temperature fused salt, comprising the following steps of: firstly, carrying out surface treatment of degreasing and oxidation film removing on strain steel matrix with a conventional method; secondly, aluminizing by adopting room temperature fused salt, wherein the room temperature fused salt for aluminizing is a system formed by AlCl3 and organic salt, the organic salt is one of alkyl pyridine halide, alkyl imidazole halide and alkaryl chloration ammonium salt, the mole ratio of the AlCl3 to the organic salt is larger than 1.0 and smaller than or equal to 2.0, the technical parameter for aluminizing by adopting room temperature fused salt is as follows: an aluminum wire as the anode has the temperature of 25-60 DEG C and the current density of 5-30mA/cm<2>, and the plating time is 30-200min; and thirdly, heat treatment to obtain an Fe-Al alloy layer, wherein the technical parameter for heat treatment is as follows: the temperature is 670-750 DEG C, and the time is 30min to 24h; fourthly, oxidation, wherein the technical parameter for oxidation is as follows: the temperature is 670-1050 DEG C, the time is 1-200h, and the oxygen partial pressure is 1.0*10-2 Pa to 2.1*104 Pa. The invention is suitable for preparing tritium permeation preventing coatings on surfaces of special-shaped pieces such as the inner wall of a pipeline, and the like, is suitable for the requirement of large-scale industrialized production, and has a self-healing function.