In this paper, two typed steel beam-column connections (Welded Unreinforced Flange-Bolted Web (WUFB) connection, Bolted Unstiffened End Plate (BUEP) connection) with and without reinforced concrete slab were experimentally examined under impact loadings. The impact tests using drop-hammer were carried out to simulate the dynamic behaviour of structural progressive collapse. The influence of slab effect and connection type on the impact resistance of steel frame substructure was discussed. The failure modes and the dynamic responses of the impact load and deformation time histories as well as the dynamic rotation and energy dissipation of the substructures were investigated. Test results showed that the upper flange of all specimens experienced local buckling near the plastic hinge section, while no welding seam cracked. For two composite connections, the cracking and crushing of concrete slab as well as bending deformation of steel studs were measured. Two composite beam-column connections had good rotation abilities and impact loading resistances, and their ultimate rotations were not less than the FEMA350 design limits. The ductility and energy dissipation of two composite beam-column connections were improved, which were better than those of bare connections. The finite element analysis (FEA) models of beam-column connections were also established using ABAQUS software. The internal force development of connections during the impact loading was examined and the parametric analysis results showed that the slab effect and connection type had a profound influence on the formation of catenary action of beam-column connections under the dynamic progressive collapse scenario.