The invention relates to a portable insulation shielding fabric flaw testing method. The portable insulation shielding fabric flaw testing method is characterized by comprising the steps that firstly, high-definition image collecting is carried out on insulation shielding fabric, and flaw parts are marked; secondly, whether the insulation performance of the flaw parts meet the standard or not is detected in a gradually-pressurizing mode. A flaw testing instrument comprises a suspension support, a handheld lighting scanner, a double-coordinate numerical control infrared laser locking device, a combined control box, a display screen and a permanent magnet probe. The handheld lighting scanner is used for collecting a high-definition image of the outer surface of the insulation shielding fabric. The image is displayed through the display screen, and the combined control box is used for measuring the insulation performance by changing the voltages applied to the two sides of the permanent magnet probe. By means of the insulation shielding fabric flaw testing method and the testing instrument, the problems that observation conducted merely through the human eyes is inaccurate, and the flaw parts cannot be scientifically measured through a megger are solved, the shielding fabric with the potential insulation issue can be detected out, the personnel safety of live line working personnel is ensured, the advantages are obvious, and the insulation shielding fabric flaw testing method and the testing instrument are suitable for application and popularization.