Abstract: To enhance the confinement effect of the precast UHPC shell and improve its bond performance with concrete, corrugated metal ducts (CMD) was adopted as permanent inner form to develop a precast UHPC-CMD formwork. A concrete column confined by the precast UHPC-CMD formwork, hereinafter referred to as a precast UHPC composite column, was fabricated. Full-section compression tests and core concrete compression tests were conducted to investigate the failure mode and the variation laws of axial-compression performance indices, including bearing capacity, stiffness, ductility, and energy dissipation. The results show that, under axial loading, the CMD in the precast UHPC-CMD formwork improved the interfacial bond performance with UHPC and concrete, enhanced the overall integrity of the specimen, and enabled the outer precast UHPC-CMD formwork to provide effective confinement to the core concrete, thereby improving the axial-compression performance of the precast UHPC composite column. The bearing capacity and peak displacement increased by 4.1% and 44.6%, respectively, with continuously increasing energy dissipation. After adding core concrete and longitudinal reinforcement to the precast UHPC-CMD formwork of the full-section compression specimens, the bearing capacity and stiffness increased by 145.07% and 93.13%, as well as by 930.74% and 55.15%, respectively. Under the same design parameters, the locally compressed core concrete specimens exhibited a longer load-holding displacement stage and further improved mechanical performance, with the load-bearing capacity and ductility coefficient increasing by 18.18% and 2.85%, respectively, while the stiffness decreased by approximately 9.1%. In addition, the confinement contributions of UHPC, CMD, and spiral reinforcement at the peak point were quantitatively evaluated, and the compressive strength of the triaxially confined core concrete under different configurations was clarified. Based on the superposition principle, a formula for calculating the axial compressive load-bearing capacity of this type of precast UHPC composite column was proposed, demonstrating high calculation accuracy.