Using molecular dynamics simulation, we investigated the mechanism by which the intercalation of a surfactant solution reduces the contact thermal resistance of two solid surfaces. We constructed a model system where two solid surfaces with a gap were immersed in a surfactant solution, and the gap was filled with permeating molecules to form a molecular thin film. By varying the concentration of the surfactant and the distance between the confining surfaces, factors affecting the intersolid heat transfer were explored. It was demonstrated that the overall thermal resistance of the present system was determined by interfacial thermal resistance between the solid and the solution and can be reduced by increasing the surfactant concentration. The surface separation, i.e., the distance between the two solid surfaces, had a significant impact on interfacial thermal resistance, whether or not surfactant molecules were involved. Interfacial thermal resistance was an oscillatory function of the surface separation and displayed minimum values not at the most adsorption amount of liquid molecules but when the density profile of liquid molecules showed a sharp peak, i.e., when the surface separation was commensurable with the size of the solvent molecule. This tendency was most remarkably seen when the liquid film was composed of a single molecular layer. The findings in this study provide helpful insights into the reduction of interfacial thermal resistance utilizing surfactant solutions.