The invention relates to a bonding agent for a microcrystalline alumina ceramic grinding tool and a preparation method thereof. The bonding agent comprises the following components according to molar percentage: 45-65% of SiO2, 5-20% of Al2O3, 10-30% of B2O3, 8-20% of (M1) 2O, 0-8% of (M2) 2O, 1.5-2.5% of ZnO, and 1.5-2.5% of XF, wherein one or more raw materials adopt nanoscale particles, ZnO and XF are added to increase the liquidity of the bonding agent, and the bonding agent is prepared by calcination, water quenching, drying and ball milling. The bonding agent is stable in performance, good in wettability for microcrystalline alumina abrasive, high in reaction capability, low in initial melting temperature, and can be used for firing a high-strength ceramic grinding tool at the low temperature of 700-800 DEG C. The prepared microcrystalline alumina ceramic grinding tool is good in grinding performance, and can be widely used in the fields of iron and steel, machinery, buildings, aviation, military industry and the like.