The value of potential barrier of H abstraction from hydrogeneted diamond (111) surface is critical to understand nucleation and growth dynamics of diamond film under the condition of Chemical Vapor Deposition.The previous theoretical works on the value are far from accord based upon different MO methods.On use of a series of cluster models and some kinds of MO methods the potential barrier is systematically studied here.After determinating the MNDO approach reliability for this problem,the corrected theoretical value is given as well.