Ultrafine rare-earth oxides (REOs) are widely applied in all fields of daily life,but the conventional preparation methods are limited by a long procedure,low efficiency and severe environmental pollution.Our team has independently developed a jet pyrolysis reactor for the preparation of ultrafine cerium oxides,and this process has theoretical significance and practical application values.In this study,gas-solid pyrolysis reactions inside the jet-flow pyrolysis reactor were numerically simulated.We performed a coupling computation of the combustion,phase transformation and gas-solid reaction on Fluent and userdefined functions.We characterized the flows of different phases as well as the compositions and distributive laws of the reactants/products in the reactor.The gas-phase inlet velocity and dynamic pressure/additional pressure were related by a quadratic function.The velocity at the throat inlet changed the most,and the outlet velocity was very stable.The CeO2 concentrations were obviously stratified.This study enriches theories of jet-flow pyrolysis and theoretically underlies the optimization and popularization of self-developed pyrolysis reactors.