In Cyber Physical System (CPS), data protection is considered as an important factor when sensors are employed in hostile environment. The sensors are highly prone for security threats like compromised nodes, who’s crypto keys embedded in the security chip are physically captured by adversaries easily. Compromised node attack are launched by the attackers by physically capturing the cryptographic keys in remote region and becoming the internal node. Traditional protection mechanisms are mostly based on cryptography, which failed to address this kind of threat. Trust Management Mechanism based on rating, ranking, weight schemes help in building a secure, flexible and available system and provides second level of security for such compromised node attack. This paper presents a dynamic trust management mechanism for Cyber Physical System based on Dirichlet Reputation System (DTM-CPS). The simulation result shows that, this DTM-CPS has a better performance and security for CPS than traditional trust management mechanisms.