The invention relates to a method and a device for detecting lead seal water ingress corrosion of a high-voltage cable. The method comprises the following steps of: winding tin foil paper at the leadseal of a high-voltage cable, coating the outer layer of the tin foil paper with an inflated bag and blowing gases into the inflated bag until the inflated bag is fully expanded; releasing the gases in the inflated bag, and taking out the tin foil paper for standby; winding the tin foil paper at the lead seal of the cable, coating the outer layer of the tin foil paper with the inflated bag and blowing gases into the inflated bag until the inflated bag is fully expanded to allow the pressure in the inflated bag to be maintained for a while; releasing the gas in the inflated bag, and taking outthe tin foil paper; and comparing the two sheets of the tin foil paper, and employing pressure deformation to determine the lead seal water ingress corrosion conditions of the cable. The method and the device for detecting lead seal water ingress corrosion of the high-voltage cable employ the pressure deformation generated after the aluminum metal in the aluminum sheath of the cable to rub the deformation through the tin foil paper and the inflated bag with no need for peeling off the plastic outer sheath of the cable so as to achieve the non-destructive detection function of the water ingresscorrosion of the high-voltage cable.