A direct numerical simulation (DNS) on a turbulent free-surface flow has been carried out to grasp and understand a gas-liquid interaction mechanism that is very important for the environmental problems and the industrial devices. The multi-interface advection and reconstruction solver (MARS) developed by one of the authors is applied to a turbulent free-surface flow. The initial velocity ratio of the gas- to the liquid-flow is assumed to be 100. The free-surface is deformed by the high shear stresses between two flows. Many ripples and small waves are generated on the free-surface and some of them are growing up to the big waves. Finally, many small ripples on the long wave, some breaking-up waves, some liquid-droplets in the gas flow and some bubbles in the liquid-flow are observed. The statistics of the turbulent quantities for the turbulent free-surface flow are presented. According to this preliminary computation, it can be summarized that the turbulent energy at the free-surface is mainly produced by the fluctuating wavy-motion of the free-surface and the turbulent convection, i.e., the fluctuations of surface-curvature and the high velocity change in the free-surface region.