The invention discloses a method for preparing metal titanium, cobalt and boron carbide mixed thermal spraying powder slurry; first of all, 61.4% of Ti powder, 15% of Co powder and 23.6% of B4C powder are added to a ball mill, at the same time, anhydrous ethanol accounting for 60-100% of the total weight of the raw materials is added into the ball mill for wet milling; the particle size of the raw material power reaches 1 to 10 micron; deionized water is taken as the solvent, and under the effect of a mechanical blender, dispersant A15 and binder PVA which account for 0.25-2% and 2-3% of the total weight of the raw material power respectively are added into the ball mill for full stirring, so that the dispersant can be fully dispersed in the slurry; the following steps are spray drying granulation and classified processing. The invention solves the problem of bad liquidity of slurry in the process of spraying granulation caused by big density difference and has simple technical procedures, regular powder shape, good sphericity and liquidity, as well as improved productivity; the product is used for reactive spraying, and the powder deposition efficiency and the coating performance will be greatly improved.