Mineral surfaces can alter the capacity of soil humic substances for binding hydrophobic organic contaminants. In this paper, two types of organo-mineral complexes of red soil and kaolinite bound respectively with humic acid were prepared. The sorption isotherms of naphthalene by the two complexes were nonlinear significantly, n=0.76 and/or 0.74, and the organic carbon-normalized sorption partitioning coefficient (Kadsoc) values of naphthalene by experimental determination were 5 times higher than the Koc values by theoretical calculation with simple Kow partitioning models. This shows that the sorption affinity of naphthalene to humics can be enhanced by the sorption of humics on the mineral surfaces of red soil and kaolinite. Moreover, the red soil is slightly stronger than kaolinte in affecting the sorption affinity of naphthalene to humics. The mainreasons seem to be that, besides kaolinite, red soils contain iron oxide minerals that can strongly bind humics, and the changes might occur in composition and conformation of the humics adsorbed on mineral surfaces, which is in favor of the sorption of naphthalene on these organo-mineral complexes.