A design method of PID controllers for stabilizing a single-input single-output multiple-time-lag system comprises the following steps: firstly, an industrial control system is used for identifying a papermaking production process with low-concentration paper pulp delivered into a headbox serving as input and the thickness of manufactured finished product paper serving as output, so that a multiple-time-lag model of a controlled system is provided; secondly, a unit feedback control mechanism is adopted, a stabilization set of all the PID controllers which can guarantee stability of a closed-loop system is calculated in combination with a modified Nyquist stability criterion and a generalized Hermite theorem on the basis of model parameters of a controlled target, a frequency upper bound omega* which is large enough is selected first, the largest permitted stability range of a proportional gain kp is calculated, then, the largest permitted stability range of the proportional gain kp is traversed, a stability range of (kd, ki) is provided for each transversal point kp according to necessary and sufficient conditions for stabilizing the multiple-time-lag system, and therefore a stable set of (kp, ki, kd) is obtained. According to the design method of the PID controllers for stabilizing the single-input single-output multiple-time-lag system, the controller target can keep running in a stable state as long as control parameters are selected from the obtained stable set of the PID controllers and a PID control program is executed, and stable control over the system is realized.