The invention particularly relates to a design and setting method for an active disturbance rejection control system of a time delay system. According to the method, based on the active disturbance rejection technology, firstly, complex controlled objects are fit into a one-order inertial element plus dead time delay mathematic model, meanwhile, time delay comes down to the disturbance quantity, a time delay reduction linear extended state observer is applied to estimation of unknown total disturbance including the time delay, active compensation for the influences of the total disturbance on the system is achieved, the time delay system is restored into a system in an integrator tandem type in an ADRC standard, and then compensation for the time delay system is achieved; finally, a closed-loop transfer function of the system is deduced, a dead time delay link in a characteristic equation is eliminated, and the numerical relationship between an ADRC single-parameter setting formula with universality and adjustable parameters is correspondingly provided. The simulation result verifies that designed practical ADRC has good stability, rapidity, accuracy and disturbance rejection.