Based on the requirements of durability and bond strength of concrete,the present design codes for concrete hydraulic structures set the minimum thickness of concrete protective layers while give no requirements for the maximum protective layers.For board or beam structures with piles,to facilitate construction,increasing the protective layer is often applied to prevent the break off and bend of reinforcement when meeting with piles.Based on present standards,this paper analyzes the engineering example,and concludes that the optimal maximum protective layer over reinforcement is between 100mm and 150mm.The conclusion can be reference for future reinforcement design of port and waterway engineering works,especially the design of high pile wharf in the coastal area.