The invention relates to a high voltage distribution line electromagnetic interference determinator and belongs to the field of distribution equipment. The determinator comprises an electromagnetic interference tester, a casing and a stretching support, wherein the casing is internally provided with the stretching support, the stretching support is equipped with the electromagnetic interference tester, and the casing comprises an upper casing and a lower casing which are connected together. Through the determinator, difficulty in measuring electromagnetic interference and electromagnetic radiation is reduced, and the determinator is suitable for being used by most people. Through the stretching support, measurement work of the electromagnetic interference tester can be more conveniently carried out, the framework formed by the stretching support is suitable for being taken as a shielding region, electric power work personnel of high voltage lines is convenient to dispose related equipment in the shielding region, interference of the high voltage lines on the equipment can be avoided, and small-distance position change of the tester can be realized through the buffer effect of a cylinder.