The composite RC (reinforcement concrete) beam featuring ultra- high performance concrete (UHPC) butterfly webs represents an innovative structural design that combines the strengths of both RC and UHPC materials. It exhibits considerable potential for applications in arch bridges. This paper presents the outcomes of a trial design involving a composite RC structure with UHPC butterfly webs. Subsequently, it conducts a preliminary analysis of the mechanical behavior of this composite RC beam with UHPC butterfly webs un der axial and shear forces. The study evaluates the effects of various parame ters, including the dimensions of the butterfly web, ratio of axial compression stress to strength, ratio of shear span to depth, and reinforcement of web, using finite element software (ABAQUS). The results indicate that the mechanical behavior of the composite beam is significantly influenced by the parameter of the butterfly web. Remarkably, the shear capacity of the composite beam in creased within the angle ranged of 50° to 70°, the thickness ranged of 40 mm to 90 mm, and the width-to-height ratio ranged of 0.9 to 1.1. Furthermore, the shear capacity of the composite beam can be effectively enhanced by optimizing the ratio of axial compression stress to strength and by designing an appropriate reinforcement configuration. It’s important to note that decreasing the ratio of shear span to depth led to a more pronounced brittle failure mode in the composite beam, but is also resulted in an increased shear capacity.