The computation is carried out to study the flow around the conical deceleration structure used in Inflatable Reentry and Descent Technology (IRDT). The calculation model is based on the Finite Volume Method (FVM) to solve the N-S equation, and the two-temperature non-equilibrium model is used to calculate the thermochemical reaction. The non-catalytic wall and full catalytic wall are considered in the boundary conditions. In order to verify the accuracy of the algorithm, the blunt body standard model ELECTRE is simulated, and the results are compared with flying test data. The calculation case of conical deceleration structure is performed with a height of 70km and the inlet Mach number is 13. The results include the variations of temperatures and chemical component concentrations along the stagnation line, as well as heat flow and pressure distributions on the structure surface. In addition, The simulation results of four conical deceleration structures with different half cone angles are compared to analyze the effect of the change of half cone angle on the surface heat flow and pressure. The present calculation results can provide reference for IRDT scheme design.