Cryptography based security solutions are not enough for WSNs when there are attacks from interior, which are caused by compromised nodes. Trust management can deal with this problem efficiently, and enhance the security, reliability and impartiality of the system. This paper gives a detailed introduction to the characteristics, the taxonomy, and the design of the framework, the vulnerability analysis, the attack models and the countermeasures. Among which the design of the framework, including the trust factors, the computation models and the application of trust, is the core of a trust management system and is given a deep insight into. In the end, several typical trust management systems are introduced. A panoramic view and detailed analysis of current trust based systems in WSNs are given.