The China Initiative Accelerator Driven System (CIADS) subcritical reactor uses a superconducting proton linear accelerator to form a periodic pulsed proton beam, which excites the periodic external neutron source to realize core operation. To study the influence of the periodic pulsed proton beam on the power control of the core, a lumped parameter method is used to establish a nonlinear model of the reactor core, which is then transformed into a linear model. Considering the periodic nature of the pulsed proton beam, the duty ratio of the proton beam is introduced to represent the duration o...