The invention relates to the technical field of detection, evaluation and authentication, in particular to a nuclear safety three-stage high-density polyethylene (HDPE) pipeline detection method whichcomprises the steps of visually inspecting the appearance, wherein working personnel inspects the inner and outer surfaces of multiple pipelines; testing the volume: carrying out butt-welding on pipeline ports of two pipelines, and using an ultrasonic technology for testing the welding part of the two pipelines; and testing water pressure: carrying out water pressure testing on a pipeline systemformed by the multiple welded pipelines. According to the nuclear safety three-stage HDPE pipeline detection method provided by the invention, through visual inspection of the appearance, volume testing and water pressure testing, three-defect detection is carried out on the pipelines, and inner and outer surface defects of the pipelines, internal defects of welded junctions and potential internaldefects of the pipelines are eliminated, so that the problems of breakage and leakage due to the defects of the pipelines are effectively solved after the nuclear safety three-stage HDPE pipeline runs; and compared with the prior art, the nuclear safety three-stage HDPE pipeline has the advantages of safety, reliability and long service life during running.