This paper tries to improve the attitude control ability of the unmanned helicopter.The fal function is not smooth at the inflection pointwhich may cause system chatteringand the system gain is large when the error is large.To solve the problemsan improved fal function is proposed to rewrite the nonlinear error feedback lawand it is re-applied to Active Disturbance Rejection Control (ADRC) to obtain an improved ADRC.Based on the established dynamics model of an unmanned helicopterthe attitude angle tracking and anti-jamming simulations under white noise and step interference are conducted on Matlab/Simulink.The simulation results show that: 1) The improved fal function is smoother at the inflection point; and 2) The ADRC based on the improved fal function still has good response speed and low overshoot in the attitude angle tracking of the unmanned helicopterand its anti-jamming ability is better than that of the traditional ADRC.