Based on statistical mechanics for classical fluids,the general expressions for the elastic moduli of inhomogeneous fluid are derived and expressed as functionals of density functions.Within the framework of classical density functional theory,the bulk modulus of confined argon in slit pore is calculated under different conditions.The effects of vapor pressure,temperature,and pore width on modulus are calculated and investigated.Obvious confinement-induced effect has been observed in the confined argon.In addition,the solvation pressure dependence of the bulk modulus is also investigated,and the results suggest that the Tait-Muaghan equation is still valid for the confined fluids.