Now, it is well known that stable diamond growth and etching of graphite can berealized simultaneously under low pressures, but it is difficult to explain by classicalthermodynamics.Based on the non-equilibrium thermodynamic coupling theorem. low-pressure diamondgrowth can be explained clearly as follows:The change of Gibbs free energy (G) is the criterion of reaction direction at constant tem-perature and pressure. Therefore, Now, it is well known that stable diamond growth and etching of graphite can be realized simultaneously under low pressures, but it is difficult to explain by classical thermodynamics. Based on the non-equilibrium thermodynamic coupling theorem. Low-pressure diamond growth can be explained clearly as follows : The change of Gibbs free energy (G) is the criterion of reaction direction at constant tem-perature and pressure. Thus,