Abstract: A preparation method and an application of a tailings-based zeolite@carbon dots-titanium dioxide (CDs-TiO2) composite photocatalyst are provided, which relates to the field of solid waste utilization technologies. The preparation method includes performing an acidification treatment on tailings powder and then roasting to obtain modified tailings powder; adding the modified tailings powder and titanium dioxide into lye to obtain mixed suspension; stirring and aging the mixed suspension under ultraviolet irradiation to obtain an aged suspension, performing a hydrothermal reaction on the aged suspension to obtain a product, filtering, washing and drying the product to obtain the tailings-based zeolite@CDs-TiO2 composite photocatalyst.