The invention discloses a preparation method of a titanium dioxide pigment for water-based paint, and belongs to the field of chemical engineering. The method comprises the following steps: carrying out dry grinding; carrying out wet grinding; screening; coating a membrane; washing and drying; and vaporizing gas. A silicon component and a boron component are added in a wet grinding process. Compared with the prior art, the silicon component and the boron component are added in the grinding process, so that titanium dioxide can be ground to certain fineness and concentration, the size of the titanium dioxide pigment on the original particle is maintained, and aggregation caused by coating the film among titanium dioxide particles is also prevented; and meanwhile, the transmissibility of light on the surface of the titanium dioxide also can be improved, and the glossiness in a using process is improved.