The bridging stress of fibers along the crack surface plays an important role in analyzing the tension behavior of short or long fiber-reinforced composites. This paper uses the inclusion theory to obtain the expression of bridging stress for short fiber reinforced composite (SFRC). A simplified model with periodically distributed fibers is proposed to estimate the average fiber spacings. The total fracture resistance is calculated as an energy summation including interface debonding energy dissipation, frictional sliding work between fibers and matrix, strain energy increment of fibers and matrix. The bend over point (BOP) stress is calculated by this fracture resistance. The necessary conditions of the fibers and matrix for the multiple cracking in SFRCs are discussed and the expression of ultimate external stress is derived. The critical fiber volume fraction for the strain hardening response is determined by an iteration method. In the meanwhile, the average spacing between two short fibers is proposed by a periodical distribution assumption. The theoretical prediction is compared with experimental data.