The invention provides a high pressure water autorotation telescopic and adjustable type in-pipe tensioning executing mechanism. A rack is formed by fastening a fixing plate and four cylindrical guiderod screws; a tensioning mechanism is formed by mutually hinging a fixing sliding block, a driven sliding block, a driving sliding block and a link mechanism; a hydraulic motor driving assembly consists of a hydraulic station, a main pushing oil cylinder, a hydraulic motor and a planetary gear; a telescopic executing mechanism consists of a hydraulic cylinder with range, an oil cylinder rod guiding mechanism, an oil cylinder rod, a high pressure nozzle, a spring adjustable mechanism, a fixed rolling wheel protection mechanism and a cage sleeve; a fixed end of the main pushing oil cylinder isfixed on a fixing plate of the rack; the fixing sliding block is fixed at the other end of the rack; the hydraulic motor driving assembly penetrates through the fixing sliding block; the hydraulic motor drives the rotary telescopic executing mechanism to rotate wholly by the planetary gear;the hydraulic cylinder with range drives the high pressure nozzle to be telescopic for cutting a steel pipe.The high pressure water autorotation telescopic and adjustable type in-pipe tensioning executing mechanism has the advantages that the construction is convenient, the mechanism can be applied to cutting of special-shaped steel pipes, the structure is simple, the operation is safe, the service life is long, and the like.