In order to clarify the effect of different interfacial shear connection arrangements on the flexural performance of ultra-high performance concrete （UHPC） composite beams， an experimental study on the flexural performance of three steel-UHPC composite beams with different interfacial stud arrangements was completed. A nonlinear analysis method for the flexural performance of steel-UHPC composite beams based on a cross-sectional fiber model is proposed and the corresponding calculation program is compiled. The applicability of the method and program is verified by the test results. The influence of the cluster degree and shear connection degree on the flexural performance of steel-UHPC composite beams is analyzed through the developed models. The results show that： 1） For steel-UHPC composite beams with cluster degree γ≤0.5 and γ=1， the critical shear connection degrees are 0.9 and 0.74， respectively； 2） The flexural stiffness of steel-UHPC composite beam increases with the increase of the shear connection degree， but decreases with the increase of the bunching degree； 3） The shear connection degree has a significant effect on the flexural capacity and ductility coefficient of steel-UHPC composite beams. The ductility coefficient of composite beams with cluster degree γ=1 increases obviously， but when cluster degree γ≤0.5， the ductility coefficient is basically no longer affected by cluster degree. 4） For fully shear connected composite beams， the shear distribution at the interface tends to be uneven with the increase of shear connection degree at the ultimate limit state， but the cluster degree has little influence on the shear distribution at the interface at the ultimate limit state. The cluster degree γ of the steel-UHPC composite beam should not be greater than 0.5， and the shear connection degree η should not be less than 1.0.