We propose a method to calculate the number density distribution of liquid molecules or colloidal particles near a substrate from the force curve measured with surface force apparatus. The method can also calculate the pair potential between the substrate and the liquid molecule or the colloidal particle. Other than the force curve, the required inputs for the calculation are the bulk number density and the radial distribution function of the liquid molecules or the colloidal particles. The number density distribution of the sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles on the mica surface has been successfully revealed using the method.