In order to solve some difficult control problems like underactuated, nonlinearity, multivariate and strong coupling in quadrotor system, a cascade control system is designed. In this control system, the classical proportion differential control method is applied in the position control loop, and linear active disturbance rejection control and nonlinear active disturbance rejection control are used in the attitude control loop separately. The two methods are compared by simulation and the simulation results show that although both methods can implement the position control and the attitude control, the linear active disturbance rejection control is better in line with the actual requirement of the engineering and more effective in quadrotor flight control.