Abstract: Early transformer substation outdoor trusses are all structured in reinforced concrete.Du to the structure feature of the concrete,technical limit and construction quality in the old days,with years' operation,corrosion of craze and peeling wildly appears on the surface concrete of these trusses which seriously affects transformer substation's operation and safety.A research on this corrosion is done and pointed out that the machanism of the corrosion is the overall effect of concrete's carbonization,alkaline aggregate reaction,corrosive media corrosion,and reinforcing steel bar corrosion.It also gives the method about how to clean and patch those corrosive positions and shows us wrapped anticorrosive treatment.Specific engineering practice has proved the correctness of the research on the corrosive mechanism as well as the feasibility and validity of the anticorrosive treatment.