The invention discloses a binder used for 3D printing materials. The binder is composed of a component A and a component B at a mass ratio of 2-3:1; the component A comprises, by mass, 50 to 60 partsof acrylic emulsion, 30 to 40 parts of polyvinyl alcohol, 10 to 13 parts of polyvinyl acetate emulsion, 8 to 15 parts of non-ionic polyacrylamide, 20 to 40 parts of soybean protein glue, 2 to 3 partsof sodium hypochlorite, 7 to 12 parts of sodium dodecyl benzene sulfonate, 15 to 20 parts of inorganic gel, 5 to 8 parts of hydroxypropyl methyl cellulose ether, 3 to 6 parts of a stabilizing agent, and 3 to 5 parts of a thickening agent; and the component B comprises, by mass, 35 to 45 parts of polylactic acid, 15 to 20 parts of aerosil, 30 to 40 parts of wax maize starch, 10 to 15 parts of ethylene glycol diacetate, 20 to 35 parts of alumina sol, 8 to 13 parts of allyl methacrylate, 15 to 22 parts of absolute ethyl alcohol, 5 to 8 parts of anhydrous potassium carbonate, 15 to 25 parts of anhydrous magnesium sulfate, 2 to 4 parts of glycol, 5 to 9 parts of nanometer manganous oxide, 3 to 5 parts of a composite initiator, 3 to 6 parts of a curing agent, and 6 to 11 parts of an activator.