This paper proposes a material model of steel fiber reinforced concrete (SFRC) subjected to dynamic loadings on the basis of an orthotropic concrete model. The effects of strain rate and fiber reinforcement are taken into account in the material model of SFRC from the uniaxial stress-strain relation to the triaxial strength envelope. The compressive and tensile strains as failure criteria are developed by reflecting the dynamic material properties, respectively. In particular, the post-cracking response according to steel fiber addition is investigated to improve the accuracy of the blast analysis for SFRC structures, and the proposed model is implemented as a user defined material model in LS-DYNA. The numerical results are compared with the experimental data in terms of damage pattern and average diameter of the damaged area for RC and SFRC slabs under explosions. The plastic based concrete models of K&C and CSCM are additionally compared to predict the behavior of SFRC structures. Furthermore, parametric studies are conducted with the proposed model to investigate the effects of reinforcement spacing and steel fiber on improving the structural resistance of SFRC slabs.