An experimental study of gas velocity distribution in the riser of a circulating fluidized bed was carried out in a cold flow Plexiglas model. The gas-velocity distribution is essential not only for design and scale-up but also for optimization of circulating fluidized bed reactors for fossil energy applications. Tests were conducted in a circulating fluidized bed riser with a diameter of 200 mm and a height of 5.5 m. The experimental results showed that the local gas velocity varied with radial position, elevation, solids circulation rate, superficial velocity and particle size. The particle circulation rates were found to have a significant influence on the gas velocity profiles. An empirical relationship for gas velocity distribution in the circulating fluidized bed riser was obtained based on the particle circulation rate, superficial velocity, and particle diameter.