Abstract:  Deepwater drilling blowout is considered to be the most serious threat in the process of deepwater oil and gas exploration and development. Choosing an appropriate tertiary well control method plays an important role when deepwater drilling blowout happens. For the Deepwater Horizon accident, a variety of tertiary well control technologies have been adopted to control the blowout, while five of them failed. In this paper, we conduct a research based on the top kill method and bullheading method used in the Deepwater Horizon accident. The reason of failure of top kill method is given, and the operation parameters and the advantages and disadvantages of different pressure well kill pattern are analyzed. Furthermore, we put forward the factors that should be considered in the process of plan optimization, which will provide theoretical guidance for subsequent design and successful operation of tertiary well control technology.