In this paper, ultra-high performance concrete(UHPC) and ordinary concrete are prepared using undesalted sea-sand. The impact of sea-sand with varying chloride ion levels on the compressive strength, pore structure and durability of steel embedded in UHPC is investigated and compared with that of conventional concrete. The results show that the chloride ion content in sea-sand does not significantly negatively affect the compressive strength of UHPC. The critical pore radius of UHPC made with sea-sand is approximately 2 nm. Different from sea sand concrete, the porosity of sea-sand UHPC increases with the increase of chlorine content in sea-sand. Even when the chloride ion content in the sea sand is as high as 0.636%, the chloride ion permeability of the sea-sand UHPC remains negligible. The reinforcement in sea-sand UHPC is in a passive state and tends to stabilize after 28 days.