The invention relates to a coal gangue ceramsite proppant and a preparation method thereof. The proppant comprises, by weight, 30%-70% of coal gangue, 20%-65% of flint clay, 5%-10% of a sintering aidand 1-3% of a forming agent. The coal gangue is solid wastes which are discharged in coal collecting process and coal washing process, the silica content is higher, the aluminum content is lower, thecalorific value of the solid waste coal gangue is fully utilized in the preparation process, meta components of the coal gangue are completely utilized again to reduce the volume density of sintered ceramsite to better adapt to the technical demands of oil well fracturing construction, fracturing cost is reduced, and the use of high-grade bauxite resources is reduced to help to protect the environment.