Abstract: Investigated are the causes for the corrosion-perforation failure of the four pieces of tubings numbered as 1,2,3,and 4 and used for a certain water injection well on an offshore oil platform by means of macroscopic observation,and analyses of chemical composition,mechanical properties and metallographic structure.As a result it is identified that for Tubings No.1 and No.3,the failure is led by the inner corrosion,i.e.,the bacteria corrosion which is accelerated by under-sediment corrosion and the residual acid corrosion,while for Tubings No.2 and No.4,the failure is caused by the outer surface corrosion.In general it is the under sediment corrosion and the bacteria corrosion as existing in the“dead water zone”between the tubing and the casing that jointly cause the said corrosion-perforation failure.