Fiber Reinforced Polymer (FRP) sheet pile offered great potential for waterfront structural applications due to their excellent corrosion resistance and high strength weight ratio. Numerical analysis method was employed to calculate and analyze the deflection of FRP composite sheet piles. Different conditions were considered, such as flexural rigidity of the pile, rigidity of the anchor, position of the anchor, friction angle δ and surcharge on the surface of the backfill etc, and deflection properties were obtained. The results showed that the increase ratio of the maximum deflection was evident when the flexural rigidity of the pile EI was rather smaller, and the large anchor rigidity can reduce the deflection of sheet piles. With the increase of the friction angle δ, horizontal displacement decreased. When the angle of friction δ was larger, the variation ratio of deflection was smaller. The deflection had linearly proportional increase with the increase of the surcharge, and the increase ratio was nearly 2mm∕kPa. For FRP composite sheet pilings, the deflection-based design method should be adopted.