The principle aim of this research is concentrated on studying the effect of cracks and their propagations on the mechanical behavior of a steel fiber reinforced concrete (SFRC) beam. High strength concretes are being used more often due to their superior properties but these concretes have higher brittleness, which is a disadvantage. The idea of adding fibers to the concrete mixture to improve the mechanical response gives high strength steel fiber reinforced concrete (SFRC) with high toughness. The effect of steel fiber is introduced in the model by giving the concrete specified high value of fracture energy. Concrete cracking is divided into two major zones; the first one is the fracture zone (a combination of wide bridging zone effect and the cohesive microscopic cracking zone) which obeys a special law permitting the transmission of stress across the two faces of crack, this zone is considered as partially cracked concrete. When crack opening exceeds a specific value , this zone is converted to a real crack (an open crack) and cannot transmit any stress across the two faces of a crack. Using the experimental data obtained from the flexural test on notched beam loaded under three-point bending, where fracture mode I is dominated. The response of the applied load-crack mouth opening displacement (CMOD) with using fracture energy calculated by the test and the cohesive stresses corresponding to their crack openings with different values of steel fiber respectively are drawn. The results show that the fracture zone for SFRC is wider than that occurs in plain concrete for many times. The contributions of plain concrete and steel fiber are being demonstrated.