_{: This study is based on a new cleaner production process of titanium sponge by in-situ pyrolysis-pyrolysis reduction magnesium smelting, in which high purity magnesium oxide and chlorine were prepared by direct oxidation pyrolysis of gaseous magnesium chloride produced by reduction distillation. Meanwhile, magnesium oxide is returned to TiCl4 reduction after thermal reduction and chlorine is returned to boiling chlorination to realize new cycle of magnesium and chlorine in sponge titanium production. This study is aimed at the reactor for homogeneous pyrolysis of gaseous magnesium chloride with oxygen, the committed step of the circulation of magnesium and chlorine generated in titanium sponge production. The concentration and velocity fields in the reactor model were studied by numerical simulation and physical simulation. When the flow ratio of nitrogen to carbon dioxide is 6:1, the circular four-port intake mode is adopted for carbon dioxide, the gas mixing heterogeneity is 0.02, reaching the gas mixing degree.}