This paper discusses the butterfly oil terminal which is popular in port engineering. Combining with relevant domestic and foreign codes,three main points,i.e. terminal length,mooring dolphin location， and breasting dolphin location are researched by comparative analysis. Among them,the location of the breasting dolphin is the most important design issue,due to the asymmetry of the flat body area relative to the amidship. Unreasonable mooring dolphin’s location will only quantitatively affect the uniformity of mooring line tension and vessel movement,while the unreasonable breasting dolphin location will affect the berthing security. Therefore,the key points of breasting dolphin position design are elaborated through an overseas oil terminal of 50,000 to 300,000 DWT for designers’ reference.