This paper designs a robust cascade PID attitude controller for the quadrotor helicopter. Firstly, based on the near-hover dynamic model of quadrotor helicopters, dual loop cascade PID attitude controllers are designed with angular rate feedback as the inner loop and attitude angle feedback as the outer loop. Then robust compensators are added to reject the effect of external wind disturbance and the various existing uncertainties. Finally, an experimental system for attitude control is built, and the attitude holding and tracking experiments for quadrotor helicopters subject to wind disturbance are conducted. Experimental results show the effectiveness of the proposed robust attitude controller.