Aiming at the model uncertainty in system and vulnerability to external environment disturbance for the quadrotor UAV in field flight, this article uses the following ideas to solve them. Firstly, use the Newton-Euler method to establish the system model. Then, according to the inner and outer loop control structure, use the attitude command of the output of outer loop position controller as the input of inner loop attitude controller. This paper concentrates to designing of sliding mode observer controller. In addition, the stability of position subsystem proved by Lyapunov theory, the resulted conclusion state that the error converges to zero in finite time. Finally, the simulation of fixed-point control shows that the controller has fast response speed, anti-interference performance, and can track quickly and accurately.