Abstract: A method for preparing a cementing material by sintering and activating coal gangue is provided. The method includes the following steps: (1) crushing coarse-grained coal gangue to predetermined particle size; (2) fully and evenly mixing the crushed coal gangue, the composite additive and water according to a set proportion, and granulating the obtained mixture; (3) distributing, igniting and exhausting the granulated pellets in the sintering machine to obtain decarburized coal gangue sinter; (4) cooling the decarburized coal gangue sinter in a cooler; (5) crushing and finely grinding the cooled coal gangue sinter to obtain a coal gangue active mixture; and (6) mixing the coal gangue active admixture, the fly ash, the quicklime and the gypsum according to a predetermined ratio, and then carrying out injection moulding, mold removal and curing to obtain the coal gangue-based cementitious material.