In the wireless sensor network environment, the randomness, fuzziness,and unpredict-ability bring a lot of secure issues to network transactions. In order to treat this problem, by using cloud model theory, the trust model based on cluster structure was proposed. This trust evaluation approach can implement the conversion between qualitative and quantitative of trust attributes. The model simulated LEACH routing protocol, evaluating trust value of the nodes according to their own characters and can identify of selfish nodes accurately. The simulation results showed that the model can accurately and objectively evaluate the nodes, and the cloud trust model proposed here may provide a new promising method for research of trust evaluation in wireless sensor networks environment.