In this present paper an attempt has been made primarily concerned with the diffraction effects of quantum theory of liquids. The hard sphere system is treated as a reference in framing the theory of liquid. We are concerned with the evaluation of the radial distribution function of the hard sphere fluid in the semi classical limit. When quantum effects are small, then the properties of fluid are analysed in power of Planck’s constant h. Some methods have been adopted to investigate the effects of quantum mechanics on the structural and thermodynamic properties of a dense hard sphere at higher temperature. It is found that the contribution of the higher order corrections increases with density. Other theoretical approach has been also taken to investigate the properties of simple fluids through an integral equation. We critically discuss the integral equation perturbation theory and the effective pair potential for the free energy and correlation function.