OBJECTIVE：To prepare and characterize glycyrrhetinic acid （GA）nanoparticles，and to evaluate its in vitro anti-tumor activity. METHODS ：Using PVP K 30 as carrier ，GA nanoparticles were prepared by anti-solvent precipitation and freeze-drying method. X-ray diffraction ，infrared spectrum ，differential scanning calorimetry and granularity analysis were used to characterize the nanoparticles ；HPLC method was used to measure the solubility and drug-loading amount of GA in the nanoparticles. MTT method was used to assay the in vitro inhibition activity of GA raw material and nanoparticles （GA doses were 12.5，25，50，100，200 μmol/L）on human liver cancer cell HepG 2 and calculate its IC 50. RESULTS ：The characteristic peaks of X-ray diffraction and infrared absorption of GA disappeared in the nanoparticles and the endothermic peak changed. The particle size of the nanoparticles was （194.88±23.52）nm，which was lower than （2 592.33±207.51）nm of raw material. The dispersion index was 0.24±0.04，which was higher than 0.15±0.03 of raw material. The average drug-loading amount of GA was 15.99％. Moreover，the solubility of nanoparticles increased from （1.05±0.01）μg/mL to（250.00±0.15）μg/mL. The results of antitumor test in vitro showed that the cell survival rates in the group of GA raw material 200 μmol/L and GA nanoparticles groups were significantly lower than that in blank control group ，and the cell survival rates of GA nanoparticles groups （except for 12.5 μmol/L group）were significantly lower than that of same dose group of raw material （P＜0.01）. IC 50 of GA nanoparticles was 86.3 μmol/L，which was lower than 364.4 μmol/L of raw material. CONCLUSIONS：GA nanoparticles are prepared successfully ；the prepared nanoparticles have small size and uniform distribution ，and the solubility are increased and antitumor activity in vitro are enhanced.