Abstract: Structured packed bed models were established for CFD simulation of convective heat transfer under turbulence condition, and the bridge method was used to deal with the problem of point contact between spherical fuel particles, to investigate the effects of cylindrical bridge size on the characteristics of flow pressure drop and heat transfer of packed bed channels. Based on the validation of experiment results, proper bridge size range was determined. The results showed that reducing the bridge size increases the calculated pressure drop gradient results in BCC and FCC packed beds; with bridge diameter not larger than 0.1 particle diameter, bridge size does not affect the average characteristics of flow pressure drop and heat transfer evidently; it is proper to choose 0.1 particle diameter as bridge diameter for flow and heat transfer simulations inside the packed bed.