The invention belongs to the technical field of a building material, specifically to an efficient water reducer for a 3D printing house thick liquid. The efficient water reducer comprises the following raw materials, by weight part, 35-55 parts of naphthalene, 5-10 parts of glycerol triglycerate, 5-15 parts of poly(ethylene-vinyl acetate), 15-25 parts of formaldehyde, 10-20 parts of xylene and 5-35 parts of calcium carbonate. Through adoption of the efficient water reducer for a 3D printing house thick liquid, the water consumption is reduced by 15-20%, and setting and hardening of a cementing material is promoted. Through adoption of the efficient water reducer, the maintenance time is shortened, and the final product is not prone to collapse. Through adoption of the efficient water reducer, the cementing material can be saved by 5-15%, and the production cost is greatly reduced.