<p>Wireless sensor networks (WSNs) have been widely applied to environmental monitoring and smart cities. Wireless sensors need to continuously collect and transfer information for long periods without human maintenance. Therefore, improving the efficiency of information transmission is a major challenge in the design of routing protocols for WSNs, which should enable wireless sensors to conserve and balance energy of wireless sensors, while ensuring high information transmission quality. To handle the limitations of current routing protocols and achieve efficiency information transmission, a distributed Q-learning based routing protocol is proposed in this paper. In the proposed protocol, five information transmission factors, which are the information transmission distance, direction and quality, as well as the residual energy and energy consumption of wireless sensors, are considered in the Q-value function to achieve high efficiency information transmission. In addition, a selective Q-value update strategy is proposed to enable our protocol to adapt to large-scale WSNs. Simulation results show that, compared with representative existing routing protocols (RLBR, UWSN, and LQEAR), the proposed protocol extends the network lifetime by about 17% according to the last node death (LND).</p>