In order to overcome the harsh environment such as high temperature, high pressure, strong vibration, and strong impact and so on, rotary steerable rool requires high standard of communication system. Due to the advantage of the high antijamming and reliability, CAN bus technology with less connection lines and better scalability is regarded as the appropriate choice of communication among every module. A control node based on can bus for rotary steerable tool was designed, includes the design of master control module and portable firmware. The master control module, as the communication center of the upper and lower terminal, can realize the instructions transmission and data analysis.The portable firmware design guarantees the reliability and safety of the communication among each module; meanwhile, this design is easily extended to different modules. The experimental results show that this control node for rotary steerable drilling tool meets the requirement of stability and reliability in a high temperature environment (such as 125℃).