Abstract: In this paper an analytic equation for the molecular radial distribution function of liquid solutions is proposed on the basis of the properties of liquid solution, the experimental phenomena, statistical thermodynamics and some similarity between total relation function and damping oscillation. The molecular radial distribution functions for pure Lennard-Jones fluid and for liquid argon calculated by the equation are compared with the computer simulation data and the experimental data with good agreement. Excess mixing enthalpy for several binary liquid mixtures calculated by the new model are also compared with the predictions of other theories and with experimental data.