Friction modifier (FM) is widely used in the curve to suppress the damage and noise between the wheel and rail. This paper compared typical third body materials, including water, oil and FM to explore their influencing mechanism on wheel-rail adhesion and damage. Furthermore, FM samples containing different solid particles were prepared. The tribological performance of these FM samples, water and oil were tested with a twin-disc testing apparatus and a hand-push tribometer. The results indicated that the shear strength of the third body material plays a vital role in the friction. The hardness of solid particles in FM greatly influences the friction control performance of FM. The change in the hardness of the solid particles makes the FM exhibit either “lack of lubrication” or “over lubrication”, that both are detrimental to the wheel and rail interface. For FM material, it is necessary to select solid particles according to the adhesion and damage comprehensively. The most suitable particle in this paper was kaolin.