By the thermal analysis methods  thermostability of a number of aminomethyl ethers of alkylxantogenic acids, synthesized as additives to the lubricants, was investigated depending on the structure of radicals near the nitrogen and acid remains. It has been determined that the stability of ethers researched is observed in the temperature range 155–190⁰C what meets the reqcurements of load-carrying and antiwear additives. Mechanizm of thermodestruction of one ethers  – NN-di(etoxithiocarbonylthiomethyl)anizidine wasinvestigated with the product identification of its initial phase decomposition, providing high load-carrying characteristics of abovementioned compound.