The conversion process from bicyclo[4.1.0]heptatriene (BCT) to 1,2,4,6-cycloheptatetraene (CHTE) within a molecular container was studied with AM1 method, and single point energies for all stationary points were evaluated by B3LYP and HF methods. The conversion potential barrier for the encapsulation complex became smooth when compared with that for the rearrangement in free state. The influences of the inner phase of the molecular container on the conversion process were discussed.