Abstract: Based on the three-dimensional Navier-Stokes equations, computational fluid dynamics(CFD) numerical simulation was used to investigate the multi-body flow field in the first separation of tactical rocket 9M55K, where the submunition tube separate from the side of the main rocket. Numerical simulation results show that the main aerodynamic interference was caused by the head shock wave reflections of the submunition tube from the main rocket, while the submunition tube was close to the main rocket, but the action of the main rocket head shock wave on the body of the submunition tube is the main reason that makes the aerodynamic characteristics of the submunition tube varied acutely while the submunition tube apart from the main rocket. Simulation results also show that there are fairly strong aerodynamic interferences between the submunition tubes while they are closed to each other. These conclusions can be taken as basis in the overall design and the selection of separate parameters for munitions with multiple submunitions.