Inspired by the bandwidth-based active-disturbance-rejection-controller(ADRC) tuning method, a novel ADRC parameter tuning-method based on settling/observing time is proposed. A method for tuning parameters $k_p$ and $k_d$ of nonlinear controller is given based on settling time by establishing the relations between settling time and controller bandwidth. Then a parameter tuning scheme is presented for extended state observer(ESO) by introducing the conception of observing time. The proposed parameter tuning methods for ADRC not only simplify the process of the bandwidth-based method, but also extend its application. The results of simulation show the effectiveness of the proposed method.