This article investigates the consensus problem for heterogeneous multi-agent systems (MASs) subject to nonlinear disturbance. A distributed fixed-time observer is considered for each follower. The proposed observer does not need any follower to become a neighbor of the leader. An improved distributed fixed-time observer is further proposed to avoid the situation in which the leader system information is unknown. This improved distributed fixed-time observer considers the output estimation errors of itself and its neighbors concurrently. Then, the consensus tracking protocols are designed to compensate for the error between leader and follower. Finally, the effectiveness of the proposed dynamic control strategy is validated by a numerical example and further application to wireless power transfer gird.