In this paper, the formation control problem of quadrotor is studied under ideal communication condition. The quadrotor has a complex mathematical model. First, the unit quaternion method is used to describe its dynamic model and kinematic model. It is decomposed into two independent subsystems of position and attitude. The tracking error model is established by introducing the error between the ture trajectory and the desired trajectory. And then appointing a member of formation as a pilot, formation members get the geometric center position as the desired trajectory through the consistency algorithm. The back-stepping method is used to design the time-varying feedback control law for each four-rotor, so that the formation is stabilized. Finally, the effectiveness of the control method is verified by simulation experiments.