For the unmanned helicopter system， the full-degree-of-freedom control problem is studied， while ensuring that the attitude constraints are within the specified range. Considering that the characteristics of the system such as strong nonlinearity， strong coupling， under driving， and intermediate control variables need to be guaranteed to be bounded， this paper reduces the strength of the nonlinearity and coupling through the feedback linearization method， and designs the controller to directly control the three positional degrees of freedom and the yaw angle. At the same time， this paper utilizes the obstacle Lyapunov function method to locally constrain the intermediate variables to indirectly control the roll angle and the pitch angle， thus ensuring that the helicopter’s attitude is bounded. Combined with the nonlinear system control theory， the tracking error system is guaranteed to be bounded， while the system is analyzed for stability. Finally， the method effectiveness is validated through simulation examples.