In the design of an LMFBR (liquid metal fast breeder reactor), it is important to know the movement of the free surface in a tank. Thus we developed a computer code for analyzing the two-dimensional turbulent flow with a free surface based on the VOF (volume fraction of fluid) and compared the computed results with those of the experiments. The measurements of surface location were made through digital processing of video images, and the velocity distributions were measured by the particle trace method and using the laser doppler velocimeter. The flow patterns and the locations of surfaces computed by this code agree with experiments.