A wharf project in the southern area needs to be set up a large flood-relief channel in the port area. Restricted by the reclamation policy，the project has a relatively small storage yard. The surface soil layer is silt and silty soil with a thickness of about 20 m，which requires ground consolidation. We compare and select the structure of the flood-relief channel，use cement mixing piles to strengthen the soft soil foundation，recommend the steel sheet pile structure because of its fast construction speed and without foundation pit，give the reasonable suggestions for the calculation method of sheet pile strengthened by cement mixing pile，and compare and check the two strengthen schemes of sheet pile wall by PLAXIS software. The results show that the reinforced body of the cement mixing pile can be considered as a rigid body，which can avoid unsafe condition caused by excessive consideration of solid addition. The reinforcement scheme in front of sheet pile wall is more favorable than that behind sheet pile wall.