Abstract: Single-phenyl-ring Cl-substitution pattern index was adopted to describe the molecular structure of polychlorinated dibenzofurans (PCDFs),and a quantitative relationship model between the lg K_ow value and the molecular structure index of PCDFs was established by forward stepwise multiple linear regression.The results of significance test are quite satisfying (n=51,R_adj=0.871,SE=0.17334,when α=0.05,F=38.647,p=0.000).Compared with the reported MOD model based on the thermodynamic computing,this method showed better ability in distinguishing the difference among PCDFs’ molecular structures.With the established model,the lg K_ow values of the other 85 PCDFs not belonging to the modeling sample set were given.These values have not been reported in literatures.