The transition velocity between flow regimes and the particle carry-over rate at the freeboard gas exit were measured in a gas-solid circulating fluidized bed which used sand as bed materials at ambient temperature. The onset velocities of the fast fluidization and the dilute transport increased with the increase of the solid circulation rate. The particle carry-over rate at the freeboard gas exit increased with the increase of the gas velocity and the static bed height. Model considerations on the particle carry-over rate were discussed additionally.