A refined solution theory for solid solubility in upercritical fluid is developed in this paper.For a dilute solution often encountered in heavy solid／fluid binary system

an expression for the chemical potential of solute is obtained by using implifyied OZ equation.The infinitely dilute chemical potential of solute in solution is separated into three parts

the contribution of repulsive force

the contribution of local structure around solute molecule and the long range attraction force in terms of direct correlation function.Concentration effect on the chemical potential of solute is calculated by a modified Wilson model based on Kirkwood-Buffs solution theory.The approach is used to model experimental values for 45 solid／fluid binary systems from literature.The model gives an AAD 11.7％ in contrast with 14.9％ of PR-EOS with vdW-2 mixing rule for all 862 data points and for polar solvent systems the model gives much better results.The partial molar volumes of naphthalene in carbon dioxide predicted by this model are in good agreement with experimetal data．