Experimental tests were reported on the autoclave cured alkali activated slag concrete(AASC) and ordinary Portland cement concrete(OPCC), fabricated with different kinds of mixing water(tap and seawater) and sand(river sand, desalted sea sand, sea sand), immersing in simulated seawater. The results of mechanical strength development of concrete and mass loss ratio of rebar during the corrosion of rebar embedded in the concrete accelerated through electrochemical method reveal that AASC has higher compressive strength and corrosion resistance than OPCC. More sever corrosion behavior can be observed for rebar in OPCC, for the mass loss ratio increases to 50%90% at 42d, while that is only 02%15% for AASC. Meanwhile, scanning electron microscope（SEM） is also used to explore the superior performance mechanism of AASC.