CFD method was employed to investigate the radial distribution of coolants in the inlet section of rod baffle multi-tubular reactor. It was found that the reactor had poor distribution of coolants. In view of this problem, the detailed structures of incident channel, shape of baffle ring and distance between tube plate and the first rod baffle were discussed to study their effect on the radial distribution. The simulation results showed that incident channels 0#, 1#, 3#, 5# and 6# could improve radial distribution of coolants significantly, and the effect of incident channels 2# and 4# was relatively limited. The zigzag baffle ring was proved to prevent short pass near the shell wall. In addition, the radial distribution of coolants was also improved with distance between tube plate and the first rod baffle increasing from 85 mm to 242mm. The simulation results can provide guidance for designing multi-tubular reactor with rod baffles.