The utilization of sea sand to produce seawater sea sand concrete (SSC) can address the shortage of river sand resources in construction projects.Seasand Seawater Concrete (SSC) demonstrates significant advantages in addressing the shortage of river sand resources in engineering construction. However, it faces critical challenges such as high chloride ion content and corrosion-susceptible steel reinforcement. Ultra-High Performance Concrete (UHPC), known for its exceptional high strength, impermeability, and durability, faces limitations in widespread application due to prohibitively high material costs. This study proposes a novel ?precast steel-reinforced UHPC tube encased SSC composite column (RUHPC-SSC composite column) by leveraging the physical-mechanical properties and complementary advantages of SSC and UHPC. Spirally confined UHPC tubular shell acts as a permanent structural formwork for casting the SSC core, providing both confinement and corrosion resistance. Axial compression static tests were performed on 12 composite short columns, and the influence of volumetric spiral reinforcement ratio and diameter-to-thickness ratio parameters on the axial compressive performance was systematically investigated. The experimental results suggest that the failure mode of the RUHPC-SSC composite column is oblique shear compression failure, with the UHPC tube maintaining structural integrity post-failure. The peak bearing capacity of the RUHPC-SSC composite column exhibits a negative correlation with the spacing of spiral stirrups in the UHPC tube and a positive correlation with the diameter-to-thickness ratio. Compared to monolithic RSSC columns, the RUHPC-SSC composite column achieves a 139.8% increase in peak bearing capacity. The UHPC tube-spiral stirrup synergy boosts both strength and deformability of the composite column.