Abstract: The preparation of mine filling materials by the mineralization reaction of fly ash and CO₂ from flue gas not only solves the problem of large-scale coal-based solid waste stockpiling but also reduces the carbon emissions of coal-fired power plants, which is an effective technique to achieve the low-carbon and green development. In response to the problems of low reaction efficiency and low CO₂ conversion rate in the mineralization reaction, such mineralization reaction experiments of millimeter level aeration were conducted by using fly ash from Fugu Power Plant in the northern Shaanxi mining area. By the division of reaction process, the main affecting factors in each stage are identified, and an innovative technique of ultrafine-nano bubble aeration to improve the mineralization reaction efficiency is proposed. At the same time, the physical and chemical properties of ultrafine-nano bubbles are quantitatively characterized by Nanoparticle Tracking Analyzers and Zeta Potential Meter. As well as the strengthening mechanism of ultrafine-nano bubble aeration on the mineralization reaction were verified through laboratory experiments. The research results show that the mineralization reaction process is divided into three stages of slow-fast-slow according to the rate of pH value reduction. The main factor affecting the mineralization reaction efficiency in the first stage is the diffusion and dissolution rate of CO₂ gas in the slurry. While in the second and third stage, it is the leaching rate of Ca²⁺ and Mg²⁺ from fly ash. At the same time, the particle size and concentration distribution of ultrafine-nano bubbles are monitored by Nanoparticle Tracking Analyzers. According to the results, the D₉₀, D₅₀, and D₁₀ of ultrafine-nano bubbles are 207.55 nm, 122.15 nm, and 81.9 nm, respectively, and the bubbles can stay in water for up to 660 minutes. The featuring of small particle size, high concentration , long residence time in water and large specific surface area, which can enhance the mass transfer efficiency. By the measured results of Zeta potential, the Zeta potential of ultrafine-nano bubbles is found to be –14.63 to –18.05 mV, while the Zeta potential of fly ash slurry is +3.34 to +3.56 mV and they can adsorb each other to further enhance the mass transfer efficiency. Through the mineralization reaction experiments under the aeration of ultrafine-nano bubbles, it is found that the mineralization reaction efficiency of ultrafine nanobubble aeration is increased by 38.78%, and the CO₂ conversion rate is increased by 67.60% verifying the strengthening effect of ultrafine nanobubble aeration on the mineralization reaction. The research results can guide development of mineralization reactors and process flow design, promote the harmless, large-scale, and resourceful utilization of fly ash, and assist in the “dual carbon goals”.