Abstract: The principle of internal friction measurement technology was introduced, and the internal frictions of Q345 steel and 22A steel were measured by internal friction instrument. The results show that the internal friction measurement method could quickly determine the existence and content of solid solution carbon and nitrogen atoms in iron and steel materials. With the decrease of cooling rate, the content of solid solution carbon of Q345 steel with different heat treatment states increased, the SK (Snoek) peak height increased, and the SKK (Snoek-Köster-Ke) peak height decreased correspondingly. Obvious SK peak, B peak and SKK peak of solid solution carbon and nitrogen atoms were observed in the internal friction curves of 22A steel.