The flight control of three degree of freedom（3-DOF） helicopter system is studied. A H

∞

mixed sensitivity robust control method based on adaptive fuzzy theory is proposed

aiming at characteristics of high order

nonlinear

strong coupling

multi input and multi output of the system. Indirect adaptive fuzzy logic system approaches the unknown parameters in the nonlinear system

and enhances the performance of online control.Combined with H

∞

mixed sensitivity robust control control

the external disturbance and parameter perturbation are suppressed. The global stability of the system is proved by using Laypunov theory. The actual flight results show that the three degree of freedom helicopter system has good

robustness and stability

and the effectiveness and superiority of the control method is also explained.