The invention relates to a preparation method of a special photocuring bismuth-base air purification finishing agent for fabrics, which comprises the following steps: mixing deionized water, a biomass surfactant, cage-type polyhedron oligomer silsesquioxane, monoclinic nano Bi2WO6 particles and silver nitrate in a mass ratio of 1:(0.01-0.05):(0.05-0.15):(0.02-0.1):(0.001-0.003), stirring, and adding ammonia water to react to obtain a functional reaction solution; and heating the functional reaction solution, dropwisely adding a polyurethane acrylate monomer for pre-emulsification, cooling, adding sodium azide and propanediol block polyether, heating to 60 DEG C, reacting for 2-4 hours, and regulating the pH value to 7-8. The finishing agent has favorable dispersion stability, and has favorable air purification effect when being used in fabrics; and the preparation method is simple and is suitable for industrial production.