OBJECTIVE： To prepare and characterize Ibuprofen （IBU） nano-powder， and to investigate its transdermal ability in vitro. METHODS： Using chloroform-ethanol （7 ∶ 3， V/V） as organic phase， deionized water as aqueous phase and polysorbate 80 as surfactant， the emulsification method was used to prepare IBU nano-powder. Laser granulometric analysis， Fourier transform infrared spectroscopy （FT-IR）， X-ray diffraction （XRD）， differential scanning calorimetry （DSC） were used to characterize IBU nano-powder. IBU nano-powder was compared with bulk drug in respects of saturation solubility， dissolution rate and transdermal rate in vitro. RESULTS： The optimum condition was as follows that the concentration of polysorbate 80 was 5 mg/mL； the volume ratio of water phase-organic phase was 40 ∶ 1； the concentration of IBU was 250 mg/mL； homogenate speed was 5 000 r/min； homogenate time was 2 min. Prepared IBU nano-powder was polyporous crumbly coralliform， and its chemical structure kept stable； the nano-powder changed from crystal to amorphous state； the particle size was 179.6 nm， and drug-loading amount was 8.99％； saturation solubility， dissolution rate and transdermal rate of IBU nano-powder were 148， 1.23 and 4.08 times of bulk drug. CONCLUSIONS： The prepared IBU nano-powder shows good water-solubility and percutaneous permeability.