As the three wheel taxiing stage of an Unmanned Aerial Vehicle (UAV) is the most vulnerable in whole flight process, this paper explores linear modeling and a gain scheduling control method of nose wheel steering turning for a tricycle-undercarriage UAV in taxiing on the ground. The force of three wheel taxiing of the UAV was analyzed, and its nonlinear mathematical model was established considering the effect of engine torque, thrust misalignment and ground angles. Then, the nonlinear model was linearized using small perturbation theory under reasonable assumptions, and the transfer function was deduced by using the nose wheel steering angle as a input and the yaw rate, yaw angle, and lateral deviation as outputs. The three gain scheduling control law through nose wheel steering turning was designed. Finally, the method was verified through a field taxiing test. The result shows that the most lateral position deviation is 0.3 m and the most yaw deviation is 4.5° under an initial yaw deviation of 3° and a lateral position deviation of 0.2 m during the process of taxiing from rest to the speed of 32 m/s. Moreover, the crosswind disturbance of not more than 4.6 m/s was inhibited. The control law designed by using the method above is robustness to the uncertain factors of the runway, tire cornering stiffness and tire deflection and has been applied to a practical UAV successfully.