Abstract： A third-order tracking differentiator and a third-order extended state observer (ESO) with an inverse hyperbolic sine function were proposed in this paper. The control law was designed with this function and the second-order derivative of the desired input signal. A new active disturbance rejection controller(ADRC) was constructed. Moreover, the asymptotic stability at the equilibrium point of the ADRC system was proved with the Lyapunov function. Finally, the simulation experiments demonstrate that the ADRC second-order system can track the square wave signal and sine signal in higher precision by rejecting the inner and outer nonlinear disturbance， and the ESO can accurately estimate the inner and outer disturbance.