A mathematical model is developed to describe the gas transfer in the grid zone of a jetting fluidized bed. The model treats the mass exchange coefficient as a fitting parameter, and is used to calculate the concentration distribution of gaseous species. The results are compared with the experimental results measured in a bench-scale jetting fluidized bed at high temperature using inert He gas as a tracer. The experiments were carried out by varying gas velocity from the nozzle and bed temperature. The gas flow rate from the distributor was kept at the minimum fluidization level. Based on experimental results published in literature, a correlation for gas exchange coefficient is proposed. The prediction coincides with the experimental results when gas percolation from jet to annulus is taken into account in the model.