Abstract: Objective To prepare osthole-PEG6000 solid dispersion in order to improve osthole dissolution rate in vitro and also improve its bioavailability. Methods The preparation methods of osthole-PEG6000 solid dispersion and the ratio of drug were screened by apparent solubility，dissolution rate and differential scanning calorimetry (DSC) spectra.The state of osthole in carrier of osthole -PEG6000 solid dispersion was further determined by using differential scanning calorimetry (DSC) and scanning electron micrograph (SEM). Results The osthole -PEG6000 solid dispersion which was prepared by melting method（the ratio of the drug to PEG6000 was 1:4）showed 60 min dissolution rate of 89.2% was far higher than osthle 60 min dissolution rate of 56.2%. The drug and carrier form a eutectic in solid dispersion and the majority of osthole existed in solid dispersion as amorphous forms or molecular state. Conclusion The dissolution rate in vitro of osthole -PEG6000 solid dispersion which was prepared by melting method（the ratio of the drug to PEG6000 was 1:4）is higher than the dissolution rate in vitro of osthole.

Key words: osthole, solid dispersion, PEG6000