In this paper, the channel characteristic of communication disturbance observer (CDOB) based bilateral teleoperation system is analyzed. It is pointed out that this method is a tradeoff between the 4-channel and the 3-channel algorithm. By the analysis, it is visible that the CDOB based approach expresses a 3-channel dynamic characteristic, because the position channel gains are seriously weakened, and the force gains are amplified for the master side in low frequency domain. Besides, the stability condition analysis is carried out for the 3-channel structure and the CDOB based method, which is helpful to design the parameters for these methods. According to this, it is pointed out that there should be enough damping in master robot if contact occurs with hard environment. Experimental results prove the discussion.