To study the factors and regularities affecting the penetration depth of steel target subjected to impact by deflagration-driving-type nail, the penetration process of 20 mm thickness Q235 steel target by 7 mm diameter nail was studied with numerical simulation. The Johnson-Cook constitutive model and the Gruneison state equation were used to simulate the penetration process of nails into steel target based on LS-DYNA finite element software, and the rationality of this model was verified through penetration test. Using the established simulation model, the influences of the cone angle of the nail’s nose, material strength of the nail, deflagration driving force, and the initial gap between the nail and the steel target on the penetration depth of Q235 steel target were analyzed. Results indicate that with the increase of the cone angle of the nail’s nose and the increase of penetration resistance, the maximum speed of the nail was decreased, so the penetration depth and the effective penetration depth were continuously reduced. When the static yield strength of the nail was less than 700 MPa, the penetration depth was relatively shallow due to the obvious mushrooming deformation of the nail, and when it was higher than 700 MPa, the static yield strength of the nail had little effect on the penetration depth. When the pressure produced by the deflagration was less than 150 MPa, the penetration depth increased approximately linearly with the increase of pressure, and when it was higher than 150 MPa, the stress was released due to the deformation of the back of the target plate, and the penetration depth was significantly improved. With the increase of the initial gap between the nail and the steel target, nail could achieve higher velocity before touching the target plate, and the penetration depth was increased, but when it was more than 20 mm, the initial gap no longer affected the penetration depth.