Thestudyonretentionbehaviorinsupercriticalfluidchromatography(SFC)isnecessarytounderstandthemechanismofthevariousinteractionsinSFC.TheretentionofSFCincarboxylicacidmethylester/polymethylsiloxane/CO2systemwasstudiedsystematicallyandtheretentionbehaviorofthiskindofcompoundsundervarioustypicaloperationconditionswasdescribedusingthemethodofanalternativeunifiedtheoryofchromatographicretention.Theresultsillustratedthatexpression:Ink.=a+b/T+cp+dp/T+ep2/Tcanbeusedtodescribequantitativelytheretentionbehaviorofcarboxylicacidmethylester/polymethylsiloxane/CO2systemintherangesofreduceddensityfrom0.549to1.411.Itwasalsofoundthattheentropyofsoluteinstationaryphaseisdependentonthedensityofsupercriticalfluid(SF)undertypicaloperatingconditionsofSFC.