For steel–concrete composite structure, a new type of stud–PBL composite shear connector can improve the shear resistance of steel–concrete interface, and polypropylene fiber ceramsite concrete can reduce the self-weight. Therefore, investigating the shear behavior of stud–PBL composite shear connectors for steel–ceramsite concrete composite structures bears significance. In this study, static testing and numerical simulation of the composite shear connector push-out specimen of polypropylene fiber ceramsite concrete were first conducted. The influencing factors of the shear bearing capacity were then analyzed. The formula for determining the shear bearing capacity of the steel–ceramsite concrete composite structure stud–PBL composite shear connectors was ultimately established. The results indicated that the new composite shear connector exhibited excellent shear resistance and good deformation ability. In addition, increasing concrete’s strength, stud’s diameter, and perforated plate’s thickness could significantly improve the shear bearing capacity of the composite shear connector. The calculated value of the shear bearing capacity of the composite shear connector was well correlated the measured value of the test. Overall, the stud–PBL composite shear connector could effectively improve the interfacial shear bearing performance of the steel–ceramsite concrete composite structure. Moreover, the established formula demonstrated broad applicability.