Abstract: In order to study the influence of soil moisture content and dry density on the penetration resistance of the projectile, the Mohr-Coulomb yield condition of soil was modified by introducing moisture content and dry density, the dynamic spherical cavity expansion theory of material was deduced, and the target resistance function was obtained. Based on this, experiment data in existing research were calculated, and they were and compared with the data in this experiment and other empirical formulas. The results show that the radial stress decreases with the increase of water content and increases with the increase of dry density in the process of penetration; compared with the results of empirical formulas and other models, the calculation model considering the dry density of water content has better prediction accuracy and can be used for the calculation of penetration depth of low-speed penetration soil.