A security model for smart terminal based on trusted levels measure named stTLM is proposed for effective solving user privacy protection and trusted communication between entities. Based on a lightweight trust levels metrics mechanism, the model can provide a fine-grained security access authorization performance by grading tasks and integrating reward-punishment mechanism. The evaluation result shows that the stTLM model has an excellent environment adaptability and dynamic performance. The model is easy to implement and be able to enhance the safety of the smart terminal effectively in open environment.