In recent years, with the rapid development of China's infrastructure and green high-performance concrete, as well as to achieve carbon peaking and carbon neutrality goals, the demand for green high-performance mineral admixtures is increasing. Ultra-fine composite mineral admixtures were meticulously crafted through the synergistic ultra-fine grinding of secondary fly ash and S95 mineral powder, incorporating varying ratios and a strategic quantity of grinding activator. This study delved into the fineness, specific surface area, fluidity ratio, setting time, activity index of these admixtures, the comparison with the main commercially available ultrafine powder, along with their application potential in cement and concrete. The findings underscore the remarkable performance of the admixtures, with a specific surface area reaching 780 ㎡/kg, an activity index soaring to 118%, and a fluidity ratio exceeding 112%, all exceeding the technical benchmarks set for S95 and even approaching S105 mineral powder standards. When 20% of P·O42.5 cement was substituted with the ultra-fine composite mineral admixtures, the resulting composite cement exhibited a marginal extension in setting time, a marked enhancement in mortar fluidity, and a substantial boost in compressive strength at both 3 and 28 days. Furthermore, the admixtures demonstrated exceptional versatility in concrete applications, with a maximum addition of 170 kg/㎥, constituting 45% of the total binder content. Notably, upon replacing an equivalent amount of S95 mineral powder and reducing cement dosage by 50-140 kg/㎥, the workability of the concrete was significantly improved, accompanied by an increase in compressive strength at 3, 7, and 28 days. Given their exceptional economic performance and multifaceted benefits, the ultra-fine composite mineral admixtures hold immense potential for widespread adoption and promotion in the construction industry.