The Hunan International Exhibition Center (HIEC) is a large space building. A stratified air-conditioning system on the second floor of the building has been adopted. Due to some problems with the air supply jet diffuser, CFD simulations were carried out to predict air distribution. Meanwhile, field measurement results were used to validate the CFD simulation results. A good agreement of simulated and test results was obtained. Based on simulation results, some analyses and suggestions are put forward to improve air distribution.