Small-scale unmanned helicopter has a peculiar flight feature of vertically take-off and landing, fixed position hovering, flying in low velocity, forward flight, rearward flight and so on. It is mainly used for civilian and military field with the advantage of light weight, low price and small scale. However, the small-scale unmanned helicopter is a strong coupled, under actuated, multivariable, time varying, open-loop unstable and high order nonlinear system. It is a great challenge to realize the research of its autonomous flight. Aiming at the internal uncertainties and large disturbance of the small-scale unmanned helicopter, a controller for yaw channel based on linear active disturbance rejection controller (LADRC) was proposed to realize the high performance control. Firstly, the yaw model of Trex—600 unmanned helicopter was analyzed and deduced, and the gust model was introduced to simulate the actual flight environment. Then, the principle of LADRC was elaborated and the yaw control system was designed based on LADRC of second order. In order to obtain the appropriate control parameters, the novel artificial bee colony algorithm was applied to conduct parameters tuning. Lastly, a trajectory tracking simulation and experiment were used to test the proposed controller compared with the PID controller. The results showed that the LADRC controller had the ability of good robustness, fast response and high control precision. The yaw angle of the Trex—600 unmanned helicopter can track the referenced trajectory fleetly and accurately.