Abstract: The oxidative decoloration of 35 anionic water-soluble azo dyes was carried out by using photo-catalytic system based on ferrioxalate complexes(Ⅲ)/H2O2.The quantitative relationship between the decoloration rate and molecular structure of azo dyes was studied by selection of molecular descriptors and multi-linear regression analysis.The results indicate that good linear correlations exist between decoloration rate of azo dyes and their molecular descriptors,in particular,MW/S and number of azo groups have most prominent contribution to the decoloration rate.The equation of quantitative relationship between decoloration rate of azo dyes and their molecular descriptors derived may be used for calculation of predicted decoloration rate.