Abstract: Continuous circulation drilling technology is a new technique appeared recently and it can realize a continuous circulation of drilling fluid during joint connection and column erection. The continuous circulation of drilling fluid is accomplished through the opening and closing of different ram cavities in closed cavity made of a group of blowout preventers. The thesis determines the overall structure of blowout preventer and introduces design of bolted structure without the side door; design, trial manufacture and testing of wear-resisting front seal; design of slip ram; design of ram status detector; manufacturing of the whole machine prototype; and situation of field tests. The field tests indicate that the BOP stack can achieve expectant goal basically. In the end, the thesis puts forward the further improvement direction according field test of circulation drilling system.