Exploiting cellulose-derived levulinic acid (LA) in biorefinery has potential application prospects, and the development of efficient and stable catalysts is crucial yet challenging. In this study, a bimetallic synergy strategy was proposed to construct an efficient and durable solid acid catalyst with crystalline solid solution by a totally solid-phase method. Mechanical activation (MA)-treated precursor (metal salts, starch, and urea) was calcined to obtain a stable biomass-derived carbon (BC)-supported AlZr (MA-AZ/BC) composite, which was applied for catalytic conversion of cellulose to LA in aqueous-phase system. The results indicate that the synergistic effect of bimetallic crystalline solid solution and the existence of Brønsted-Lewis dual-acid sites in the MA-AZ/BC catalyst contributed to a cellulose conversion efficiency of 97.5% and a LA yield of 67.1%. Benefiting from the strong bimetal-support interaction, the MA-AZ/BC catalyst exhibited favorable stability and recoverability. On the basis of comprehensive analysis, a reaction mechanism of Brønsted-Lewis dual-acid sites for synergistic catalytic conversion of cellulose was proposed. This study provides a new idea for the rational design and environmentally friendly fabrication of functional BC-based catalysts for efficiently producing platform compounds derived from biomass.