The Pebble Bed Water Reactor (PBWR) has attracted wide attention due to its outstanding advantages in the inherent safety performance, high conversion efficiency and low power density design. In this paper, the RPI wall boiling model was applied to solve the local flow and heat transfer of subcooled flow boiling in a pebble-bed channel. The effects of inlet subcooling on the flow and heat transfer characteristics are carefully analyzed. It is found that fluid velocity is lower in the corner between adjacent pebbles, leading to deterioration of heat transfer. So the wall temperature was higher near the contact points of the adjacent pebbles. The bubbles began to grow near the contact points between adjacent balls. Reducing the inlet temperature would delay the onset of boiling and the area of boiling region was getting smaller. This study can provide useful information to the design of the PBWR.