Abstract: Greenhouse effect has been received more and more attention in the field of environment protection recently. N2O is an important geenhouse effect gas, whose effect is 206 times stronger than that of CO2. Some researches show that beacuse of coupling relationship and competition effect between different trace gases, other trace gases can affect N2O′s life and ozone′s depletion speed in the atmosphere. In order to give an instructive theoretical reference to experimental researchers, AM1 molecular orbital methods using the restricted Hartree-Fock (RHF) calculation have been applied to investigate the mechanism of the reaction of H2O2 with N2O. The results show that this is a multistep reaction. Along the reaction path there are two transition states, one internal rotational barrier and two intermediates. The step from Re to IM1 is the ratecontrolling step, whose activation energy is 323.04 kJ•mol1. The whole reaction is exothermic, with the heat of formation equals to －147.67 kJ•mol－1.