The ability to resist at chloride ion penetration and compressive strength of ocean high performance concrete (HPC) with nano-SiO₂ (NS) addition was studied. The 6 hours direct current coulometry method (6-hours DC Method) in ASTM C1202-97 was adopted. The experimental results show that the ability to resist at chloride ion penetration of HPC including NS is heightened effectively, the charge through high-performance concrete with 3%, and 5% NS is reduced with 5% and 15% respectively, and the ability to resist at chloride ion penetration can be heightened gradually with of the age; the charge through high-performance concrete with NS decreases with reducing of W/B of concrete.