Abstract: B3LYP/6-311G(d,p) theory and MP2/6-311G(d,p) theory  were used to calculate the Hetero-Diels-Alder reaction’s mechanism of oxime and cyclopentadiene.The results indicate that C—N bonds’ formation was prior to C—C bonds’;the formation and fracture of C— N bonds and C—C bonds were asynchronous collaborative processes；C=O bond which was passivated did not participate in the reaction.Reactions agree with frontier orbital theory which is favorable for the hetero-Diels-Alder reaction’s  progress.From the perspective of thermodynamics and kinetics,the reaction is feasible and the optimization results are of great significance.Reaction’s calculated data is in full agreement with literature’s.

Key words: oxime, cyclopentadiene, Hetero-Diels-Alder reaction, B3LYP, MP2