The invention belongs to the technical field of buildings, and relates to double-pressure-holding power down-set pile driver. The double-pressure-holding power down-set pile driver comprises a pile driver seat, wherein the pile driver seat is provided with a drill stem system and a pressure holding system capable of driving the drill stem system to lift along the vertical direction, the drill stem system comprises a drill bit mechanism and a lengthened rod mechanism consisting of at least one lengthened rod, a down-set power head mechanism capable of driving the drill bit mechanism to rotate along the circumferential direction is arranged between the drill bit mechanism and the lengthened rod mechanism, and the pressure holding system comprises a primary pressure holding mechanism and a secondary pressure holding mechanism of which axes are overlapped and which can tightly hold the lengthened rod mechanism. By adopting two pressure holding mechanisms, the continuous drilling operation can be realized, the operating efficiency is improved, the power output is uniform, and the engineering quality can be guaranteed.