Abstract: In order to develop the carbon mineralization technology of coal fly ash, coal fly ash-based high-efficiency carbon-negative materials were prepared in this study, and the application effect of their mineralized CO₂ products in different cementitious material composites was explored. In this study, the mineralization products were added to the ordinary Portland cement, sulfoaluminate cement and building gypsum building materials according to the substitution ratio of 5% and 10%, respectively, and the mechanical properties and hydration products of the cementitious composite were tested and the microstructure was analyzed. The experimental results show that after carbonization, the AFt and C-S-H, which is easy to carbonize, decreases significantly, and the content of calcium carbonate increases significantly. When the curing reaches 28 days, the compressive strength of the test blocks with 5% and 10% substitution ratios can be increased by 32.5% and 24.2%, respectively, and the XRD results show that most of the CaCO₃ in the composite exists in the form of calcite. In the sulfoaluminate cement composite, the mechanical properties of the mineralized products decreased slightly in the early stage, but when the curing reached 28 days, the compressive strength of the test blocks with 5% and 10% substitution was increased by 9.0% and 14.0%, respectively, compared with the mineralized coal fly ash, indicating that the mineralized coal fly ash could improve the mechanical properties of the sulfoaluminate cement composite in the later stage. In the building gypsum composite, the mechanical properties of the gypsum test block with a substitution ratio of 5% mineralized coal fly ash were improved, and the mechanical properties of the gypsum test block with a substitution ratio of 10% coal fly ash mineralization product decreased slightly, indicating that there was an optimal dosage range. The research results provides theoretical and data support for the building materials utilization of solid waste-based CO₂ mineralized products.