In this work, we consider the case, in view of the vulnerability of communication networks in leader-follower multi-agent systems, that is the attacker will launch False Data Injection Attacks against communication network. Consequently, to solve this, an effective detection mechanism for FDIAs which target at the communication network is established. In the meantime, for avoiding using false observation caused by FDIAs, Distributed Reduced-Order Extended State Observer (DROESO) is employed for mitigating the matched disturbance under contest environment because of its special principle. Finally, simulation example verify the effectiveness of the proposed algorithm.