Conducted is investigation and study on practical application situation of undersea Christmas tree at home and abroad and results show that undersea Christmas tree is a very mature technology and has been widely used in international oil and gas field exploitation, its maximum installation depth may be deeper than 2700m. At present, the technology is applied in a handful of oil and gas fields in China, its design, manufacture, installation and construction techniques are grasped by not many foreign oil companies. Up to now, there is no example of application of domestic undersea Christmas tree in offshore oil and gas field exploitation. Domestic oil companies shall seize the opportunity of cooperating with foreign oil companies and improve the abilities in design, manufacture, installation and maintenance of undersea Christmas tree so as to meet the demand of deep sea oil and gas field exploitation.