The insertion reaction mechanism of CCl₂ into CH₂O has been studied by using the B3LYP/6-311G* and CCSD(T)/6-311G* at single-point. The geometries of reactions, transition states and products were completely optimized. All the transition states were verified by the vibrational analysis and the internal reaction coordinate (IRC) calculations. The results show that the reaction (1) is the dominant reaction path, which proceeds via two steps: (i) two reactants form an intermediate (IM1), which is an exothermal reaction of 9.73 kJ•mol^－1 without energy barrier, (ii) P1 is obtained via the TS1 and the H-shift, in which the energy barrier is 47.32 kJ•mol^－1. The pressure dependences of the total rate constant were calculated by applying RRKM-TST model in temperature range from 300 to 1900 K. The statistical thermodynamics and Eyring transition state theory with Wigner correction were used to study the thermodynamic and kinetic characters of this reaction. The results show that the appropriate reaction temperature rang is 400 to 1800 K at 1.0 Atm (101325 Pa), in which the reaction has a bigger spontaneity capability, a larger equilibrium constant (K) and higher rate con-stant (k).

Key words: CCl₂, CH₂O, insertion reaction, density functional theory, thermodynamic and kinetic studies