The non-prismatic reinforced concrete (RC) beam considered a unique case in structural engineering as it has variable depth all over beam section and it doesn’t have sufficient information in structural codes, this can put structural engineers in a challenge to predict how this beam will react under specific types of loads or with different geometrical variables and strengthening existence. In this research, concrete plastic damage constitutive model developed and used to explore the shear strength of non-prismatic RC beam structure. Furthermore, in order to improve the shear strength of existent RC beams, Carbon Fiber Reinforced Polymers (CFRP) strips are attached to the surface of the critical sections. For this aim, initially numerical model was calibrated according to the data obtained from laboratory tests then a series of numerical simulations with different variables are carried out to investigate the shear behavior and these variables were: haunch angle α value and CFRP strips existence (composite status). The numerical results show that changing beams geometry (haunch angle α value) can have an influence over shear strength, in addition, using CFRP strips has an obvious effect on the failure behavior of the non-prismatic RC beam structure. Finite element simulations are executed by using ABAQUS.