The special atmosphere of oxidation and reduction combustion in regenerative heating furnace is confirmed by anglicizing working principle of the furnace, and the growth and nature of steel’s oxide layer is influenced by the special combustion atmosphere. From the respects of thermodynamics and kinetics, the high-temperature oxidation regular of 20CrMo steel is studied. The oxidative production include steady oxide of Fe2O3、Fe3O4、FeO.The oxide layer grow slowly when temperature below 1100°C, but speedily when it is over1100°C. With the commutation of valve, the combustion atmosphere of regenerative heating furnace alternates between oxidation and reduction. Following the "intermittent" growth law, 20CrMo steel is in the process of “growth - decomposition –growth”.