Kaempferol (KAE) is a strong antioxidant flavonoid compound, but its clinical application is limited by quantity and poor dissolution property. However, the dissolution mechanism of a kaempferol nanoparticle formulation (KAEN) has not yet been elucidated. The aim of the present study was therefore to use a nanoparticle engineering process to resolve the dissolution problem. Our data indicated that KAEN effectively increased the dissolution percentage by particle size reduction, high encapsulation efficiency, amorphous transformation, and hydrogen-bond formation with excipients. In addition, we used several different antioxidant activity assays to evaluate KAE and KAEN. The data indicated that KAEN retained potent antioxidant activity after the nanoparticle engineering process and showed better antioxidant activity than KAE dissolved in water (P < 0.05). According to these findings, we concluded that KAEN could be a low-dose alternative to KAE in health food and future clinical research.