Abstract: Based on statistics, a new equation shown below was derived to represent the physical adsorption on solid surfaces after modifying the assumptions used by Langmuir for deriving the equation of monomolecular adsorption: or, n= where n amount of adsorption per unit weight or per unit area of solid; p(or C) pressure of gas or concentration of liquid substance; K, b0 & M constants with physical meanings as described in this paper. This equation can be used to represent satisfactorily the five types of physical adsorption as reported in the literatures. Under certain conditions, it can be shown that this equation can be transformed into two widely used empirical equations, one proposed by Freundlich and the other by Temkin.