Abstract: The mathematical model based on Computational Fluid Dynamics (CFD) technique is developed for the direct current arc plasma jet reactor in order to optimize the reactor structure and operation conditions for the direct production of acetylene from coal by thermal plasma technique.In this model, fluid flow, convective heat transfer,and conjugate heat conductivity are considered simultaneously on the basis of rational assumption. It avoids the error caused by estimating the temperature of inner wall of the reactor. Realistic allowance is made for turbulent behavior, temperature- dependence property value,and boundary conditions.The thermodynamic and transport properties of H₂/Ar system, which are usually expressed in the tables of discrete data, are fitted into the expressions that can be easily inserted in the program.Simulations of turbulence is carried out by commonly used standard k-ε two equation turbulence model.The temperature field and velocity field in the plasma jet reactor are calculated by using SIMPLEST algorithm.The conclusion obtained provides guidance for further experiment and technical development.