To defend against internal attacks in wireless sensor networks (WSNs), building a trust model between sensors nodes has been proved to be an effective way in this paper. The most current trust models only consider communication behavior when calculating direct trust, which is directly calculated based on the interactions between sensor nodes. However, this is not enough because of the various types of attacks. Furthermore, the adverse effect of poor-quality links on the trust value of normal nodes is not discussed in the current trust models. In this paper, we propose a beta and link quality indicator (LQI)-based trust model (BLTM) for the WSNs. First, communication trust, energy trust, and data trust are considered when calculating direct trust. Then, the weight of communication trust, energy trust, and data trust are discussed. Finally, an LQI analysis mechanism is proposed to maintain the accuracy and stability of the trust value of normal nodes in a network with poor-quality links. Compared with other models, e.g., beta-based trust and reputation evaluation system (BTRES), the simulation results show that the BLTM can defend against internal attacks, e.g., DoS attack and data tampering attack which the BTRES cannot resist and can reduce the adverse effect of poor-quality links on the trust value of normal nodes effectively.