The invention relates to a preparation method of a concrete waterproofer which is mainly applied to the field of the architecture industry, and concretely relates to the preparation method of the concrete waterproofer with an industrial by-product gysum non-calcining technology. The preparation method comprises the following steps: carrying out simple dehydration on the industrial by-product gysum until water content is below 10%; preparing material powder with diameters of less than 200 meshes by modifying through a Raymond mill; mixing the industrial by-product gysum powder, semihydrated gypsum, alum and kaolin according to a proportion of 3-5:0.5-2:2-4:1-3; and ball milling to the fineness of less than 200 meshes. The concrete waterproofer prepared in the present invention has a high efficient water-reducing and reinforcing function, allows the pore structure of the concrete to be effectively improved and gel to be precipitated simultaneously to block capillary channels in the concrete, so the impermeability is improved 5 to 8 times compared with conditions with no waterproofers, the waterproof effect is permanent, the heat release rate of cement hydration can be delayed, concrete cracking can be effectively prevented, and 10% of cement can be saved.