In order to study the forming factors of the rod shaped jet in the hemispherical shroud, the forming process was numerically simulated by nonlinear dynamics software AUTODYN-2D. The analysis of outer radius of curvature, hemisphere cover height, wall thickness and charge length/diameter ratio of the four factors on the velocity of jet head and tail rod speed difference influence of orthogonal design on the basis of research on the influence of four factors of rod like jet head velocity and tail velocity difference between primary and secondary, optimal combination and get through the data processing of every level of four factors. The results show that with the charge ratio of length to diameter, radius of curvature, sub hemisphere hood cover high increase and decrease the sub hemisphere cover thickness of the rod head and tail jet speed difference increases; the charge length / diameter ratio is the main factor affecting the head velocity, radius of outer curvature head speed with minimal impact cover; high is the main factor affecting the head velocity difference, outer curvature radius and wall thickness on the head and tail velocity difference has little effect. The research can provide reference value for structural optimization of rod jet.