Abstract: Under internal solitary ocean waves, a cylindrical drilling platform would drift, which could affect the efficiency and safety of operations on the platform, so the accurate prediction of internal solitary wave load is critical. Based on the application conditions of the theories of three kinds of internal solitary waves (KdV, eKdV and MCC),the scale effects of internal solitary wave load of a cylindrical drilling platform were analyzed through numerical simulation for the strong nonlinear action of internal solitary wave in a two-layer fluid, and in model tests. The results showed that it was feasible to calculate horizontal and vertical forces of internal solitary waves in large scales by using the Morison formula and Froude-Krylov formula. In addition, in the model experiments of internal solitary wave load demonstrated that scale effect differences existed between horizontal and vertical forces.The scale effect was less on the horizontal force compared with vertical one due to fluid viscosity influence difference.The viscosity effect on vertical force might be neglected.