Security issues of wireless sensor networks (WSNs) have become increasingly prominent. As a reasonable complement for encryption, authentication and other security mechanisms, intrusion detection technology has become an important domain of WSNs security research. So it has very academic and practical value to design an intrusion detection approach adapting to wireless sensor networks characteristics. At the basis of the reputation computing model we designed, and after analyzing features of the sensor networks intrusion detection mechanism, we proposed an intrusion detection model based on trusty nodes inside clusters make use of the reputation computing model to calculate the coordinate nodes synthetic reputation values to check whether some invasion has taken place. If some nodes are being intruded, the messages will be reported to cluster head. When the numbers of the reporting nodes are more than the specified the head will report the information to sink nodes and start intrusion response at the same time. The experimental results show that the designed models can identify vicious nodes and low competitive nodes, helping to promote the security and reliability of the network, and embodying the equity of the network.