Abstract: Steering shaft is a key component of directional rotary steering drilling tool to achieve steering drilling. When drilling, the steering shaft is subject to complex forces and is prone to vibration, which affects the steering stability, accuracy and reliability of the rotary steering drilling tool, thus affecting borehole trajectory control, wellbore quality and drilling efficiency. In this paper, the steering shaft was taken as the research object. The steering driving force of eccentric ring group, the torque of rotating jacket and the lateral force of stratum rock were analyzed and the mechanical model of the steering shaft was established to analyze the load. Based on the dynamic theory and finite element method, the modal analysis and harmonic response analysis of the longitudinal and transverse vibration of the guide shaft were carried out. The influence of the yaw angle of the guide shaft on the natural frequency of the guide shaft and the influence of the torque, the drilling pressure and the yaw angle of the guide shaft on the vibration characteristics of the guide shaft were discussed.The results show that when the yaw angle of the guide shaft increases from 0 to 6 degrees, the natural frequency of the transverse vibration increases significantly. Lateral vibration is the main vibration form of the guide shaft. The transverse amplitude of the connection between the guide shaft and the eccentric ring group is larger at the distance of 0.52 m from the guide joint. The torque and weight-on-bit have a greater impact on the longitudinal vibration of the guide shaft. As the torque increases from 1 000 N·m to 1 600N·m, the longitudinal amplitude of the guide shaft increases by about 1.3 times. The research results provide theoretical references for the design of structural parameters of guide shaft, the improvement of guidance stability and accuracy, and well trajectory control.