In order to investigate heat transfer behaviour at an individual particle scale, the particle cooling process in a rectangular spouted bed is simulated by the Computational Fluid Dynamics-Discrete Element Method (CFD-DEM). As the inlet gas velocity increases, the gas-particle convective heat transfer in the jet region is intensified, while the convective heat transfer in the annular region is weakened. The inlet gas velocity also has an influence on the particle-particle conductive heat transfer. Particle-particle conductive heat transfer in the jet and fountain regions can both be enhanced by increasing inlet gas velocity, but this variation trend is opposite in the annular region. Additionally, the temperature distributions of particle and gas phases in the bed are also analyzed in detail. Compared with the infrared thermography experiment, the particle cooling process in the simulation results agrees closely with that in the experimental results.