In order to establish the finite element grid model of the tube structure accurately and quickly, a parametric modeling method based on the Python script language operating unit and the node coordinates was proposed to establish the finite element grid model of the body tube. Through this method, the finite element mesh model of the tube bore (including the medicine chamber, the slope and the guide part) and the external contour were accurately established and parameterized. In addition, with the 76 mm artillery as the object, the finite element model of the coupling of the barrel and the projectile was established, and the full ballistic motion of the projectile was calculated and verified with the corresponding experiment. The results show that the method can accurately and quickly establish the finite element mesh model of the tube structure.