The invention relates to a method for inhibiting electrocorrosion of a porcelain insulator iron cap by use of PRTV, and an auxiliary apparatus. The method comprises the following steps: removing dirt and cement residues in a slit between the iron cap and a porcelain surface; sleeving the outer edge of the slit by use of the auxiliary apparatus; perfusing the PRTV at a perfusion nozzle of the auxiliary apparatus; and after the perfused PRTV is dried, dismounting an annular main body of the auxiliary apparatus. The auxiliary apparatus comprises the annular main body and a mold removing pad, the annular main body is shaped by laterally enclosing a band-shaped body and is formed by locking the two end portions of the band-shaped body by use of a locking device, the annular main body is provided with the outwardly projected perfusion nozzle, apart from the perfusion nozzle, the upper edge and the lower edge of the annular body are respectively attached to the iron cap and the porcelain surface correspondingly, and the mold removing pad is arranged at the inner side of the annular main body. The method is ingenious in design, simple to operate and high in practicality, thereby being widely applied to inhibition of the electrocorrosion of the porcelain insulator iron cap.