Abstract: Based on the variational principle, the differential equations are derived to calculate the interfacial shearing force of a steel-concrete-steel sandwich panel with a formula given to calculate the interfacial shearing force under uniformly distributed load. The calculated results show that the mid-span shearing force is maximum, and it decreases nonlinearly along the span gradually and approaches zero at the end. On the other hand, the interfacial shearing force increases with the stiffness of connections between the two steel plates and external load but decreases with the increasing steel content of the board and concrete strength. The main influencing factors on the interfacial shearing force are the stiffness of connections and external load.