A composition for ultraviolet light intensity detection comprises nematic mixed crystals, chiral additives, cholesteric liquid crystals, azobenzene monomers, photopolymerizable monomers and a photoinitiators. When preparing a film having the composition, the steps include mixing each of components of the composition and spreading out the mixture to form a pre-formed film of the mixture, and irradiating the pre-formed film by light to form a film for ultraviolet light intensity detection.