The particle size of medicinal materials is an important physical property that affects the pharmaceutical behaviors such as dissolution, chemical stability, and bioavailability of solid dosage forms. The size reduction of raw medicinal powder is needed to formulate insoluble drugs or slightly soluble medicines and to improve the pharmaceutical properties such as the solubility, the pharmaceutical mixing, and the dispersion. The objective of the present study is to evaluate physiological activity of amorphous and nano-particle preparations of insoluble drug, ursodeoxycholic acid (UDCA), which were made by three types of fine grinding mills. The change of physical properties of ground UDCA was conformed by Mastersiger microplus and X-ray diffraction. We have investigated hepatoprotective effects of the nano-particle preparations of UDCA by planetary mill, vibration rod mill and jet mill in CCl_4-induced oxidatively injured mouse liver. The results showed that nano-particle preparations of UDCA all decreased reactive oxygen sepecies generation and lipid peroxidation in CCl_4-induced oxidative stress mice. Among them, nano-particle preparations by vibration rod mill and jet mill showed more significantly hepatoprotective effects compared to intact UDCA and planetary millground UDCA. These results suggest that ground UDCA with vibration rod mill and jet mill shows a high amorphous state and the improved dissolution.