Abstract: The cathotic protection is a difficult topic for oil and gas pipeline to cross large river or under the water. In the paper the feasibility of sacrificial anode without ground bed to prateet pipelines under the water was disenssed. The key points to put on are the annular anode to protect the pideline with external cement layer, the special anode tape to protect inner pipe of casing pipe. As an example the design calculation, analysis of economic effects are stated.