High-strength steel has excellent mechanical properties, which has been utilized in the fields of explosion and impact. In order to study the blast resistance of high-strength steel plates, ANSYS/LS-DYNA software was first used to simulate the impact test on high-strength steel materials. By comparing with experimental results, the Johnson-Cook model parameters characterizing the dynamic constitutive behavior of high-strength steel are determined. Based on the above model parameters, the explosion simulation of high-strength steel plates under near-field explosions is further carried out. The interaction process between the explosion shock wave and the steel plate is systematically analyzed, and the size effects of the steel plate on its deformation characteristics and failure mode are explained. The results show that the Johnson-Cook model can effectively simulate the mechanical behavior of S690 high-strength steel at high strain rates. High-strength steel plates have a weakening effect on the propagation of shock waves. With the increase of steel plate thickness, the propagation range of shock wave through steel plate decreases gradually. For high-strength steel plates of different geometric dimensions, near-field explosions will cause three damage modes: petal-shaped fracture, small fracture and large deformation. It is found that the thickness is the decisive factor to determine the failure mode of steel plates under near-field explosions. For high-strength steel plates with large deformation, the increase of thickness and decrease of width will improve the ability of resistance to near-field explosions. In addition, there is a positive correlation between the ability of shock resistance of the high-strength steel plate and the width-thickness ratio. When the proportional distance is 0.13, a model can be provided to predict the maximum displacement range of the high-strength steel plate according to the steel plate size. The above conclusions can provide some guiding significance for the optimal design and engineering application of high-strength steel structures.