Abstract: The all-covered type of sheet-pile wharf is a new type structure, which makes the sheet wharf possibly be used in the construction of deep water berth. There is still no complete theory for the design of the all-covered type of sheet-pile wharf, and the spacing of barrier piles is mostly determined by engineering experience, as there is a lack of any mature method. The barrier pile is a typical passive pile. The soil arching behind the barrier piles will be formed under a certain condition. Most of the soil pressure behind the piles is transferred to the barrier piles by the soil arching, and thereby the mechanical behaviors of the front wall can be improved. Based on the assumption that soil arching effect exists behind the piles, combined with the static equilibrium equation, strength condition for mid-span section of the soil arching, and the failure condition for the triangle compression zone at the arch springing, a formula for the spacing of barrier piles is proposed.