OBJECTIVE To determine the characteristics of RP isoflavones in differens drug carrier system,including EC/PEG mixture carrier and PEG single carrier by solid dispersion technique.METHODS DSC,X-ray diffraction,IR-spectra and SEM were used.RESULTS By using solid dispersion technique,RP isoflavones was homogeneously dispersed in the drug carrier system.EC/PEG RP isoflavones solid dispersion formed a new type of material phase because of interaction between EC/PEG and RP isoflavones molecules.The PEG RP isoflavones solid dispersions formed more hydro-keys resulted by -OH in the molecules.After releasing 12 h,the EC/PEG RP isoflavones solid dispersion became much bigger,wider and soft than the material before releasing.CONCLUSION RP isoflavones was dispersed in molecular size in the carrier.PEG was the hole-making agent improving the permeability to EC-membrane,and EC had the function of dissolution and inflation.It demonstrated that EC/PEG RP isoflavones solid dispersion was an ideal drug release system,which released fast at initial and then following zero-order mechanism;PEG RP isoflavones solid dispersion was a fast release system.