Abstract: The numerical simulation of a model experiment installation was carried out for its two-channel operating conditions by using Fluent code, which was applied for design validation of hot gas mixing structure at reactor outlet of pebble-bed module high temperature gas-cooled reactor (HTR-PM). The configurations of numerical simulation, such as boundary condition, turbulent model and solving method, were confirmed by comparing the temperature, pressure and velocity profiles obtained by numerical simulation and experiment. The two-channel operating conditions of designed hot gas mixing structure at HTR-PM reactor outlet were simulated by using Fluent code according to the configurations. It is concluded that the design of hot gas mixing structure at HTR-PM reactor outlet can fulfill the requirements of high hot gas mixing performance and low pressure drop on the two-channel operating conditions.