Abstract: Comparison was conducted between the gas-liquid fluidized bed and draft-tube bioreactor (DTBR). It is found that the DTBR has higher ability and efficiency of oxygen transfering. When the surfacial gas volecity is 0. 29 cm/s, the (KLa)20 and EA of the DTBR are 1. 2 and 1. 3 times respectively as much as that of fluidized bed. The major factors which effect the mixing characteristics of DTBR were also studied . The results show that the surfacial gas velocity plays the most important role, and the surfacial liquid velocity has less effect on the mixing characteritics. When surficial gas velocity is 0. 29 and 0. 074 cm/s,the circulating time of DTBR is 12s and 16s respectively; and the mixing time of DTBR is 76. 2s and 91. 8s respecitvely.