In this paper， a novel prefabricated steel inner core-UHPC composite hollow column with a pocket connection is proposed for a novel super long-span steel-UHPC arch bridge to accommodate the span length， accelerate the construction， and reduce the self-weight and cost. The column consists of a steel inner hollow section and an exterior UHPC shell. The steel inner core can serve as the formwork of the column and provide an additional energy dissipation source. The design concept of the column and the connection details are first presented， followed by a detailed experimental program. To be specific， a 2/5-scale column was designed based on the preliminary design of the novel arch bridge and tested under the most unfavorable axial load ratio （0.24） in a pseudo-static manner to investigate the seismic performance of the proposed column， including the damage pattern， the connection performance at the interface of the prefabricated column， displacement ductility， energy dissipation capacity， stiffness degradation， residual deformation， curvature distribution and strains of the steel inner core. The test results showed that the proposed column failed in a flexural manner， including the yielding of the steel inner core and reinforced bars and crushing of the UHPC shell in the plastic hinge region； the joint remained intact and no visible crack was observed at the interface between precast and post-cast UHPC， indicating the proposed column with the pocket connection is reliable. In addition， the tested column had large equivalent damping ratios but low displacement ductility， mainly due to the mismatch between the thickness of the steel core plate and the thickness of the UHPC thin wall layer. The large axial load ratio （0.24） could be another potential cause. Moreover， the experimental results were used to validate a numerical model， on which a parameter study was performed on the novel column from the prototype bridge. The results show that the increase in the axial load ratio will result in a reduction in the ductility ratio. When the axial ratio varies between 0.05 and 0.2， the ductility coefficient of the prototype column is generally close to or larger than 3.0. The research results can provide the basis for the subsequent design and application of steel inner core-UHPC columns.