As a promising way of integrating combustion, CO2 separation, and pollution control with high efficiency and low cost, Chemical Looping Combustion (CLC) has gained attention in recent years. A cold model circulating fluidized bed reactor for chemical looping combustion was designed and operated, in which an additional loop was used to transfer back some oxygen carriers to the air reactor directly for continuous oxidation. Operating conditions of the cold model were investigated as the superficial gas velocities in the reactors and seal-loops were varied. Their effects on the pressure balance and solids circulation rates in two loops were tested. The experimental results provided a detailed mapping of the range of operating conditions and assisted in the understanding of critical variables controlling the operation of the CLC reactor system. The appropriate operating conditions were optimized for developing the reactor model for CLC.