Rule-based CPS monitoring methods have significant advantages in reducing monitoring complexity and improving monitoring flexibility. Currently, rule-based CPS monitoring methods do not consider the timing constraints of CPS monitoring scenarios, and only use various optimization techniques to shorten the response time. Based on the real-time rule engine, a real-time monitoring system of CPS, RTCPMS, is established. The system uses Rete network to represent the monitoring rules, and its core is a new real-time inference algorithm Rete-TC. The Rete-TC algorithm introduces the rule deadline, and the timing constraints of CPS monitoring is satisfied as much as possible by the priority-based Beta node scheduling method. The simulation experiment and smart building application case verify the effectiveness of the RTCPMS, and the experimental results show that the core algorithm Rete-TC has a better scheduling success ratio than the traditional rule inference algorithm Rete.