The invention relates to a method for preventing an indoor swimming pool with a concrete structure from being eroded by chlorine gas. The invention has the technical scheme that non-prestressed steel bars which are processed by an advanced hot galvanizing method are adopted in posts and a roof with concrete structures; when prestressed steel bars are adopted in the concrete structure of the roof, the prestressed steel bars adopt non-adhesive prestressed steel stranded wires; the concrete contains polypropylene fiber, the consumption of which is 0.5-2.5 kg/m<3> concrete; and the weight ratio of chlorine ions to cement in the concrete of unit volume is smaller than or equal to 0.1%. In the method of the invention, the strength grade of the concrete can reach more than C40 grade, the swimming pool with the concrete structure can be safely used within the normal concentration range of chlorine ions, and the erosion caused by environmental factors is reduced. The adoption of the polypropylene fiber can obviously improve the durability of the concrete structure, thus compared with the common concrete, the anti-leakage capacity of the concrete containing the polypropylene fiber is improved by more than 70%, and the service life of the swimming pool is prolonged and can be prolonged by more than 60%. Therefore, the invention has better application value and popularization value.