In this work, we report a bifunctional phosphor Sr₃Sn₂O₇:Eu³⁺ which shows red luminescence and photochromism properties. All as-prepared Sr₃Sn₂O₇:Eu³⁺ samples were studied systematically by X-ray diffraction, photoluminescence spectra, diffuse reflection spectra, thermoluminescence glow curves. The optimum doping concentration of Eu³⁺ for the PL emission was determined to be 0.2. Concentration quenching and thermal quenching in photoluminescence (PL) emission were discussed in detail. Meanwhile, the material can change its surface color from white to brown under ultraviolet (UV) (254 nm) irradiation. The colored sample is bleached by blue light (400 nm) irradiation or heat treatment. The coloration-bleaching process is reversible, which makes it potential to be used in the field of photo switchers, erasable optional memory medial and sensors. Finally, a model is proposed on the basis of experimental results to discuss the mechanism of photoluminescence and photochromism in Sr₃Sn₂O₇:Eu³⁺ in detail.