Abstract: Corrosion behavior and rust of low-alloy steel in natural seawater was investigated with electrochemical technology and raman spectroscopy.The results showed that low-alloy steel corrosion turned into a stable stage after 0.5 month immersion in the seawater.The difference of oxygen supply induced the rusty layer divided into inner and outer.The low-alloy steel corrosion rate can be fitted in formula V=0.3227t^-0.2489.