Abstract: In order to meet the increasingly demanding requirements for the total height and volume of blowout preventer (BOP) stack from drilling and workover technologies, particularly the special drilling requirement, the F18-21 integral BOP stack has been developed. Finite element analysis shows that the BOP shell of one-step cast meets the Equipment Specifications for Wellhead Apparatus and Christmas Tree. Various functional tests show that its shell strength, hydraulic-controlled cylinder strength, sealing property of annular rubber core, sealing property of valve plate rubber core and main path diameter all meet field application requirements. The field assemblage result shows that, compared with the conventional BOP stack, this integral BOP stack is about 500 mm shorter at height, 600 kg light at weight, and 2 places less in sealing leaking points. It is characterized by compact configuration, reliable functions and time-saving and power-saving.