The invention discloses a cesium silicate titanate photocatalyst and a preparation method and an application thereof. The cesium silicate titanate photocatalyst has the chemical formula of CsSi2TiO6.5, has a morphology of irregular particles or spherical particles, and can be prepared by using a high-temperature solid-phase method and a sol-gel method; the production cost is low, and equipment requirements are simple; the prepared cesium silicate titanate photocatalyst has the advantages of good dispersion, uniform granularity, good chemical stability, quite strong light absorption and good repeated stability, has a function of decomposition of harmful chemical substances under irradiation of ultraviolet light, and has good potential application prospects.