Abstract: The hydrodynamic force of lifting pipes in a 1 km pilot-scale mining system of polymetallic nodules is determined by many parameters. Based on the integrated design parameters of the 1 km pilotscale mining system, the suitable wave theory was selected and all kinds of parameters were presented. A numerical integration procedure was formulated for calculation of the hydrodynamic force according to the Morison equation. The relationship among the force, time and depth below ocean surface was finally studied. At the same depth below ocean surface, the total hydrodynamic force is varied with increasing time as a function of sine. While at the specified time, the total hydrodynamic force is decreased with increasing depth below ocean surface. The lapse rate is particularly fast from 0 to 200 m in depth. The maximum of hydrodynamic force is 3. 790 kN.