At present, spalling failure has begun to appear in concrete slab of high concrete rockfilled dam (CFRD). Based on known displacement on cushion surface of a high CFRD, the model including face slab and cushion was set up using submodeling technique. The effect of different joint sealing materials in vertical joint on stresses of face slab was analyzed. The results show that the two joint sealing materials mentioned in the paper can effectively decrease the maximum pressure and strain in horizontal direction. Birch board can also decrease the maximum pressure and strain in slop direction. It is helpful to prevent spalling failure in face slab. So Birch is more suitable and suggested as joint sealing material in vertical joint.