Disclosed is a pearlescent pigment for a water-based paint, comprising: a pearlescent pigment substrate, an alkyl phosphate diethanolamine salt coating coated on the pearlescent pigment substrate, a KH-792 silane coupling agent coating coated on the alkyl phosphate diethanolamine salt coating, and a trimethylolpropane triacrylate coating coated on the KH-792 silane coupling agent coating. Further disclosed is a method for preparing a pearlescent pigment for a water-based paint, comprising using a finished or semi-finished pearlescent pigment as a substrate, alternately coating a plurality of layers of organic or inorganic additive coatings on the surface of the substrate, and then performing steps of suction filtration, washing, drying, and sieving to obtain a special pearlescent pigment for a water-based paint. Additionally, further disclosed is a sieving and impurity removal device used in the preparation method of the special pearlescent pigment for a water-based paint according to the present invention.