In order to explore the reliability of the simulation of inner solitary wave generation in OpenFOAM software, a small internal wave tank is established, and the gravity collapse method is used to generate internal solitary waves for physical tests. An equal scale numerical water tank is established based on OpenFOAM, the solution multiphaseInterFoam is captured by the incompressible, adiabatic and insoluble multiphase interface of the VOF model, the air-silicone-water three phase fluid is set, and the internal solitary wave generation is simulated. The data of amplitude, waveform and velocity obtained by the numerical simulation are compared with the experimental and theoretical solutions. The results show that the simulated inner solitary wave is in good agreement with those in the physical test and theoretical solution and is of high accuracy, which can be further applied to the study of the evolution characteristics of inner solitary wave and its interaction with structures, and is of important application value in physical oceanography and military oceanography.