The invention provides a single-component water-based acrylic dispersoid and a preparation method thereof. The provided single-component water-based acrylic dispersoid comprises the following components: isopropanol, (methyl) acrylate, a vinyl monomer, an acrylic acid/or a methacrylic acid, pentaerythritol tetraacrylate, an initiator, a neutralizer and deionized water. The provided single-component water-based acrylic dispersoid is convenient to use and operate, the link of preparing paint is saved compared with double-component paint, the performance of the single-component water-based acrylic dispersoid rivals that of a middle and low hydroxyl second-level dispersoid, and the single-component water-based acrylic dispersoid has the characteristics of high glossiness, high fullness, high hardness, good water resistance, good weather fastness and the like. More importantly, the VOC (volatile organic compound) in the provided single-component water-based acrylic dispersoid reaches 0, sothat the single-component water-based acrylic dispersoid is quite environmentally-friendly.