The discharge pipe line is one of the important devices for cutter suction dredgers, while the pipes connecting to cutter, pump and valves guarantee the high dredging and transportation efficiency. The flow mixed with water and soil with different density is highly turbulent and unsteady, which induces vibrations along the pipe and also cause abrasion inside the pipe especially at bends and T branches. The flow exciting force induce the pipe stress and deformation while the pipe deformation will influence the flow pattern. Due to the large diameter of discharge pipe and lots of bends and T branches, the Fluid Structure Interaction (FSI) should be introduced for pipe dynamic analysis and supporter design. The uncertainty of the mixed flow makes it not possible to design or test all the working conditions. Therefore, the CFD technique has been employed for numerical analysis. The typical pipe lines and their supporters with specified exciting source are investigated. Modal analysis and stress results give proof for optimal supporter design and pipe line.