To address the spatial conflict between pipeline laying and the main structure in modern buildings, reinforced concrete beams with abdominal incisions are taken as the research object. The finite element software ABAQUS is used to establish nonlinear numerical models of 7 beams with incisions and 1 solid-web beam. Through four-point bending simulations, the influence of the shape, lateral position, and number of the incisions on the ultimate bearing capacity of the beams is analyzed in detail. Results show that circular holes have the weakest stress concentration effect due to the absence of sharp corner points, minimizing degradation of bearing capacity and ductility; The closer the incision is to the bearing, the more pronounced the weakening of the ultimate bearing capacity, and the failure mode shifts from ductile bending to brittle shear; An increase in the number of incisions triggers a "weakening cumulative effect", leading to a nonlinear accelerated decrease in bearing capacity and easily inducing overall brittle failure along the multi-incision connecting path. The results provide a theoretical basis for the engineering application and optimization design of abdominal incision reinforced concrete beams.