According to the characteristics of light load and high speed of the meteorological sounding rocket, the aerodynamic 3D numerical simulation of the meteorological sounding rocket was carried out. Based on a certain type of small bore large length-diameter ratio weather detection rocket, the modeling and calculation of the whole rocket were carried out, and the aerodynamic characteristics of the rocket at transonic speed were analyzed. It was verified that the high aspect ratio knife-shaped tail was feasible in the small bore of large length-diameter ratio transonic weather detection rocket. The results show that the analysis can provide a reference for the fin design of small bore rocket with large aspect ratio.