Abstract: Pebble bed reactors use “multi-pass” circulation scheme of spherical fuel element. The fuel spheres are uploaded from the core one by one, and lifted up to return to the core through the pneumatic conveying pipeline. In this paper, the motion model of impulse pneumatic transportation of spherical fuel characterized by the “approximately equal diameter” was established. Some influences, such as air supply pressure, effective area of controlling valve, sphere-to-pipe diameter ratio, etc., to the velocity of fuel elements were analyzed. The practical velocity of fuel element was measured by using speed measuring instrument fixed in 10 MW pebble bed reactor. The test results agree with the theoretical results. The establishment of the motion model of fuel element in impulse pneumatic transportation provides the foundation for the optimum design and regulation of fuel transporting system.