We have analyzed the flow in the semi-open-type nozzle for ship driven by high-pressure gas experimentally. We proposed a new finite difference lattice Boltzmann model which allows us to consider the immiscible two-phase and the different density of two fluids for numerical analysis of flow in the nozzle. We also demonstrate that this new model works well. The surface tension model was satisfied with Laplace s law. Two-dimensional cavity flows with proposed finite different lattice Boltzmann model for the different density is calculated and compared to the result by the Finite Difference Method.