<p>The comprehensive utilization of high-alumina coal fly ash (HAFA) has garnered widespread interest due to its abundant content of aluminum and silicon. Therefore, this study presents a treatment process for the utilization of HAFA by preparing Al-enriched mullite and silica products. First, HAFA undergoes low-temperature ammonium fluoride (NH₄F) activation–water leaching to remove the glass phase and recover Al-enriched mullite. This removal mechanism has been systematically investigated. During ammonium fluoride activation, Si-O bonds in the glass phase were effectively broken, and the amorphous silica was transformed into water-soluble (NH₄)₂SiF₆. After water-leaching treatment, the maximum removal rate of the glass phase was 95.65% under optimum conditions. The mineralogical phases of the water-leaching residue were primarily mullite and corundum. The refractory performance of the Al-enriched mullite met industrial specifications. Moreover, the nano-silica product (with a purity of over 97% and specific surface area of 216.85 m²/g) and a recyclable ammonium fluoride solution were produced from the desilication liquid using an ammonification process. The as-obtained nano-silica product can be used as a rubber compounding ingredient. This paper introduces an innovative approach for the integrated and high-value utilization of HAFA.</p>