In the modern building industry, the demand for sustainable and efficient construction methods is increasing, and the use of composite beams has significant advantages in terms of construction speed, cost effectiveness and structural integrity. In this study, the static bearing capacity of concrete composite beams under different stirrup structures was analyzed, including composite beams composed of prefabricated parts and on-site pouring parts, as well as a cast-in-place beam. The bearing capacity, ductility, and other properties of these beams were studied by the proportional model tests of two kinds of composite beams with different stirrup configurations. The results showed that under the same stirrup configuration, the composite beam was more prone to shear failure and its ductility was reduced. However, due to the ‘stress advance ‘effect, the steel bar stress, mid-span deflection and maximum crack width of the composite beam were significantly higher than those of the same cast-in-place beam. Additionally, when the stirrup configuration was doubled, the ductility of the composite beam was improved, but its bearing capacity was not improved.