The invention provides an adjustable phased array pipeline girth weld detection device which comprises a body, a magnetic pressing wheel mechanism, an auxiliary bracket, a tightening device, a left flaw detection probe bracket, a right flaw detection probe bracket, a left flaw detection probe and a right flaw detection probe; the body comprises a foundation support, a first sliding rod, a second sliding rod, a sliding rod jackscrew, a left sliding rod linkage frame, a right sliding rod linkage frame, magnetic wheels and wheel shafts; the tightening device is used for tightening the body onto a pipeline to be detected, the magnetic pressing wheel mechanism is arranged between the first sliding rod and the second sliding rod, the auxiliary bracket is connected with the first sliding rod and the second sliding rod of the body, and the flaw detection probe brackets are connected with the flaw detection probes and assist the flaw detection probes in conducting detection on the girth weld of the pipeline to be detected. When the device is used for detecting the pipeline girth weld, the device can rotate steadily around the flaw detection pipeline, therefore the situation that the detection result is affected by vibration and other accidents is prevented, and the device can have the advantages of being wide in applicable range, high in flaw detection sensitivity, high in detection efficiency and the like.