The invention discloses key equipment applied to the pressure test operation of a deep sea oil and gas pipeline. The key equipment comprises a pressure test regulation and control system, a chemical agent injection system, a data collection and transmission system, a pressure maintaining control system, an auxiliary system, an immersed sea water filter, an underwater pressure testing pump, an underwater throttling and control system, an underwater flowmeter, an underwater pressure gage and a pressure sensor, wherein all above systems are designed according to the application of a water depth which is greater than 2000m, the requirements of underwater antiseptic materials are met, the above systems are connected through skid-mounted modules, and the above systems are externally provided with a protection frame of a frame type structure. By use of the key equipment, all underwater arrangement of pressure test operation equipment can be realized, the defects of more ground equipment, large space occupation, high input cost, more high-pressure potential safety hazards and the like in a conventional pigging operation are reduced, and pressure test operation efficiency of a deep water pipeline is improved.