Abstract: In order to study the flexural behavior of steel box composite girders with different shear connection degrees, static loading tests were carried out on four steel box composite girders with shear connection degrees of 0.5, 0.75, 1.0 and 1.25, respectively. The failure characteristics, bearing capacity, interface slip, deflection and strain development laws of tested girders were analyzed. Taking into account the contact relationship between the studs and the concrete flange, refined numerical models of steel box composite girders were established. The influence of structural parameters on the flexural performance of steel box composite girders was analyzed. The applicability of the current code provisions to calculating the stiffness and ultimate flexural capacity of steel box composite girders with different shear connection degrees was examined. The results show that as the shear connection degree decreases, steel box composite girders exhibit an increasing number of mesh-like intersecting cracks on the top surface of the concrete flanges, longitudinal splitting cracks and bending cracks on the mid-span flanges. The interface slip at the girder ends becomes more pronounced, and the elastic flexural stiffness, yield capacity and ultimate flexural capacity of steel box composite girders gradually decrease. The load-deflection curves calculated by the numerical models are in good agreement with the experimental curves, and the numerical models can well reflect the whole process flexural behavior of steel box composite girders with different shear connection degrees. The current standards, considering the reduced stiffness calculation method for interface slip effects and the ultimate bearing capacity calculation method based on simplified plastic theory and limit equilibrium theory, are suitable for the stiffness and ultimate flexural bearing capacity calculation of steel box composite girders with different shear connection degrees.