This paper presents a dynamic model for a novel self-drive pipeline robot or "pig," which obtains its power from the kinetic energy of fluid flow in a pipe via a turbine and a reverse-traverse screw mechanism. The new robot is designed to move both against and with the flowing fluid, which makes it different from conventional "pigs", which can only move with the flowing fluid. This bidirectional capability makes it very valuable to many industries, especially the oil and gas industries. Based on the model, the dynamic behavior of the new robot under different conditions has been analyzed in detail. In order to verify the validity of the dynamic model, a prototype machine and pipe-loop test rig was built, and experimental data obtained compared well with the theoretical analyses. Both the theoretical and experimental results validated the practicability of this novel robot structure. Furthermore, detailed analysis has been carried out, and the conclusions that have been drawn provide basic design principles for this new pipeline robot, and will assist in the aim of optimizing details of its design.