Abstract: In view of the attacks of malicious nodes, a probability model based on stochastic petri net was proposed to describe the intrusion detection response behavior of cyber-physical systems. The influence of the intrusion detection response on the reliability of cyber-physical systems was analyzed. Considering the continuity attack, random attack and insidious attack, the optimal intensity of detection and the response intensity were set in order to balance the energy saving of systems and the intrusion tolerance. The results show that the reliability of cyber-physical systems is optimal by adjusting the detection response intensity according to the attack strength and the detection behavior.