In this paper, the problem of consensus control for a class of multi motor drive systems is studied. For a single pendulum system driven by six direct-current motors, a consensus protocol control design method based on a proportional integral observer is proposed. Based on H_∞ technology, the proposed observer can estimate the states of the systems and obtain the effective estimation of unknown inputs and measurable noises. On this basis, a distributed consensus control protocol is constructed. The solution of observer gain matrixes and consensus gain matrixes is transformed into solving linear matrix inequality problems. The Matlab simulation of a single pendulum system driven by multiple motors with given parameters shows that the proposed method is correct and effective.