Abstract: The study focused on the utilization of heat-pressed and stuffy slag, processed into an ultrafine vertical grinding mill. This pressed-heat and stuffy slag powder replaced traditional anticorrosion fillers, such as epoxy resin, xylene, butanol, and polyamide, therefore forming a composite anticorrosion coating. Tests were conducted to assess the hardness, adhesion, abrasion resistance, and flexibility of these coatings according to various standards: GB/T 1730—2007 (paints and varnishes–pendulum damping test), GB/T 1720—2020 (circle-drawing test of coating films), GB/T 1768—2006 (paints and varnishes–determination of resistance to abrasion-rotating abrasive rubber wheel method), and GB/T 1731—2020 (determination of flexibility of coating and putty films), respectively. Additionally, the salt mist resistance was tested in conformance with GB/T 1771—2007 (paints and varnishes–determination of resistance to neutral salt spray) and water absorption was evaluated consistent with HG/T 3344—2012 (determination of water absorption of paint film) for coatings. The contact angle, impedance modulus, and corrosion potential of the coatings were also determined using a contact angle measuring instrument, a precision impedance tester, and an electrochemical workstation. Moreover, the micromorphology, chemical composition, mineral composition, and particle size distribution were evaluated using electron microscopy, X-ray spectroscopy, X-ray diffraction, and laser particle size analysis, respectively. The research analyzed the impact of pressed-heat and stuffy slag powder on the mechanical properties and anticorrosive properties of the epoxy composite anticorrosion coatings. It found that the pressed-heat and stuffy slag consisted of C₃S, C₂S, Ca(OH)₂, C₂F, RO phase, and f-CaO possessed properties similar to silicate, thereby improving durability. The processing method using an ultrafine vertical grinding mill facilitated the mineralization of f-CaO, reducing particle size and increasing specific surface area. The study concluded that the optimal performance of heat-pressed and stuffy slag powder/epoxy composite anticorrosion coatings was achieved when the particle size uniformity was 2.240 and the addition rate was 5%. At this rate, the performance of the composite anticorrosion coating is the best, the average swing rod hardness test result is 115.75 s, adhesion reached level 3, wear was minimized, flexibility measured 4 mm, impedance modulus was 10^6.1 Ω·cm⁻², and corrosion potential (E) was 0.143 V. In summary, heat-pressed and stuffy slag, a type of rigid particle, can improve the hardness, friction resistance, and mechanical properties of the epoxy coating system. A uniform particle size can enhance the denseness and anticorrosive properties of these coatings. This opens up new possibilities for the high-value utilization of pressed-heat and stuffy slag outside of building materials and fulfilling the dual purpose of “increasing efficiency with waste” in the steel industry and “reducing cost with waste” in the paint industry.