In Device-to-Device (D2D)communications, the communication environments are multifarious and it is difficult for devices to distinguish undependable services and get successful cooperation. In this paper, we originally propose a broker-guided trust calculation model based on feedback from brokers of BSs which provide mobile network services. And we adopt lightweight trust evaluating mechanism which facilitates low-overhead trust computing algorithms to reduce networking risk and improve system efficiency. Compared with existing models, the experimental results show that our model have great advantage in both reliability and efficiency.