Abstract: In order to develop biomass fast pyrolysis reactor, an experimental equipment of spout-fluid bed with a draft tube of 0.15 m in inside diameter, and 1.04 m in height. Experiments were performed to investigate the effects of the inside diameter of draft tube, the installation height of draft tube and the length of draft tube on flow characteristics of mixing materials of spout–fluid bed with draft tube under the same cold mold experiment condition. The results show that solid circulation rate, central fountain height, bed pressure drop increase with the increment of the inside diameter; solid circulation rate and central fountain height are the maxima with the minimal pressure drop when the length of draft tube is 0.45 m; solid circulation rate is enhanced and then reduced with the increase of the installation height of draft tube, therefore the balance of spouting gas bypassing and entrainment effect must be synthetically calculated.