To enlarge the workspace and improve the motion capability of a parallel robot, the base of the robot can be guided to move along a linear or curved track. This paper aims at analyzing how the motion of the base affects the dynamics of a parallel robot. For this purpose, kinematic and dynamic equations are developed for a circular track-guided tripod parallel robot. For kinematics, the motion of the base is incorporated into the analytical formulations of the position and velocity of the tripod. For dynamics, equations of motion are derived using the Lagrangian formulation, and influence factors are defined to provide a quantitative means to measure the effects of the velocity and acceleration of the base on the actuator forces of the tripod. As an application of the above method, a circular track-guided tripod is proposed for the automatic riveting in the assembly of an aircraft fuselage. Simulation studies are carried out to investigate the tripod dynamics. It is found that the motion of the base has a strong impact on the actuator forces. The dynamic model provides a useful tool for the design and control of the circular track-guided tripod.