The present paper studies the characteristics of the foil load and the vertical motion of the high-speed ships with hydrofoils quantitatively. First, the hydrofoil load was measured directly using dynamometers. Time-domain non-linear simulation was carried out using TSLAM- F_HF ^1.2.3.4) and was compared with the experimental data. It was shown that the simulation can predict not only the vertical ship motion but also the foil load quantitatively in case no hydrofoil emergence occurs. The experimental result, however, shows the necessity of further investigation on the characteristics of histeresis of the hydrofoil lift to simulate ship motion in case foil emergence occurs. The eigenvalue analysis for the vertical ship motion of the high-speed ships with hydrofoils was performed based on the linearized equation of motion. The effect of the ship speed, the area and locations of the foils on the ship motion in wave was clarified.