Abstract: Grid fins can improve underwater vehicles attitude through the fluid forces they received, and ventilation technology can stabilize the attitude of underwater vehicles by improving their surface fluid loading. The application of active ventilation technology to the vehicle with grid fins has been expected to significantly improve the underwater vertical motion stability of vehicles. In this paper, the overlapping grid technology and six-degree-of-freedom solver were used to simulate the movement and evolution of underwater fluid field around the vehicle. Comparing with the experimental results, the accuracy of the numerical calculation method was verified, exploring the effects of ventilation installation of grid wings, and different ventilation rates on the motion stability of underwater vehicles with grid fins. The results show that ventilation and installation of grid wings can help to reduce the deflection angle during the launch process and to improve its motion stability, showing the excellent role of grid wings. And the deflection angle can decrease with increasing of ventilation rate, and when the length of the ventilation cavity develops to the position below center of mass of the vehicle, a normalizing moment opposite to the direction of the deflection angle will be generated, and if the ventilation cavitation wraps grid fins, the grid fins will be invalid. This achievement possesses an important guiding significance for underwater navigational body to install the grid wing and navigate under the condition of ventilation.