Epoxy resin is a popular choice as the matrix of organic coatings in the metal protection sector. However, the single shielding effect of epoxy coatings is limited. One effective method to improve their protective properties is to add inorganic fillers to epoxy coatings. Coal gangue with a large number of micropores and a high specific surface area, is a rich source of alumina, silica, iron oxide, calcium oxide, magnesium oxide and other components. There are few relevant reports on the application of coal gangue in the field of anticorrosion at home and abroad. Therefore, expanding the application of coal gangue in the field of anticorrosion coating may be of significance in environmental benefits, technical application and innovation. Herein, the impact of coal gangue addition on the performance of epoxy coatings was studied with epoxy resin E44 as matrix and different proportions (1%, 5%, and 10% in mass fraction) of coal gangue as fillers to prepare coal gangue-modified epoxy resin coatings. These coatings were subsequently applied to silica gel plates and Q235 mild steel surfaces, yielding samples of free coating film and coated steel. The average coating thickness was approximately 150 μm. The morphology of coal gangue powders was revealed by means of JSM-7001F field emission scanning electron microscope as that the coal gangue presented multi lamellar structure with an average particle size of 3.18 ± 0.12 μm, which may be conductive to the improvement of the coating properties. Then, a series of tests were conducted to assess the performance of the coating, including a water absorption test, tensile test, adhesion test and electrochemical EIS test. The results showed that the addition of coal gangue to the epoxy resin in proper quantity can enhance the densification, strength, toughness, adhesion and anticorrosive properties of the coatings. However, the performance improvement showed non-linear dependence on the dosage of coal gangue; an excess addition of coal gangue can result in particle agglomeration, which may lead to an increase in defects, and reduction in the protective properties of the coating. For the coating with the addition of coal gangue 5%, the fracture strength reaches 35.30 MPa, the maximum strain reaches 6.13%, and the lower saturated water absorption rate of 2.24% can be obtained after immersing for 10 d. This is accompanied by a loss of adhesion of 58.65%, maintaining the maximum low-frequency impedance modulus value of 3.40 × 10⁸ Ω·cm² and the maximum coating resistance of 6.36 × 10⁷ Ω·cm². The multi lamellar structured coal gangue with large specific surface area and anisotropic multi-orientations of grains, which may be beneficial to the enhancement of the densification, further the mechanical properties, the adhesion, and the anticorrosive properties of the coating as well. The coal gangue serves as a filler, and its additive mass fraction of 5% represents the better performance of the coating. The utilization of gangue in anticorrosive coating represents a novel avenue for the effective deployment of coal gangue and the diversification of filler types in anticorrosive coating. The composition and distinctive microstructure of coal gangue permit the optimization of coating performance through the implementation of appropriate modifications.