In this paper, a new approach is proposed for predicting reaction force in simply supported steel fiber reinforced concrete (SFRC) beams under impact loading (drop weight test) considering the energy conservation approach. If SFRC beams completely fail under impact load, it can be found that the total reaction force is equal to force capacity of SFRC beams. The force-deflection relationship can show the peak force that the SFRC beam can carry under impact load. Since concrete is a material sensitive to loading rates, the strain rate of loading and also the volume fraction of steel fiber will influence the beam’s response. The force-deflection relationship of the SFRC beam under impact loading is obtained using the proposed model. This model considers the effect of volume fraction of steel fiber and also the strain rate on the concrete properties. The model is then verified with the results collected from the literature that include 189 SFRC beams tested under drop-weight impacts and included in a database. The results obtained show that this method can estimate the maximum impact force with acceptable accuracy.