The circulating system of slurry shield is the core system used to transfer the excavated pebbles from the tunneling face. The flow characteristics of pebbles in the circulation pipeline are the keys to smooth transportation of the pebbles. The simulated motion model in the horizontal straight pipe of the slurry shield circulation system is established based on computational fluid dynamics and discrete element method; and the influence of shape factor, the equal volume particle size and pebble number on the pickup velocity of pebbles are studied. The simulation results show that: （1)When the equal volume particle sizes of the pebbles are the same, the pickup velocity of pebbles with ellipsoid shape is the largest, followed by that with flat shape and that with nearspherical shape is the smallest. （2）The pickup velocity of the pebble exponentially increases with the equal volume particle size of pebble increase. （3）The pickup velocity of pebble logarithmically increases with the pebble number increase; while the pickup velocity of multi particles gently increases with the pebble number increase, and the maximum increase reaches 21%.