The invention discloses an ageing testing device for insulating paper of a power transformer. The ageing testing device comprises an oil tank, a heat radiator and a circulating pump, wherein an oil outlet and an oil inlet are formed in the bottom of the oil tank; a circulating channel is formed among the oil tank, the heat radiator and the circulating pump; the oil tank is internally provided with an insulating paper bracket with a cylinder structure; the insulating paper bracket is fixedly arranged in the oil tank through a connection rod; heating temperature control units are uniformly distributed on the surface of the insulating paper bracket; an oil taking opening for sampling is formed in the side face of the oil tank. The ageing testing device and the ageing testing method for the insulating paper of the power transformer have the characteristics of simplicity in operation, capability of simulating the operation state of solid insulation in the transformer, capability of improving the operation temperature of the solid insulation in oil to accelerate ageing, capability of simultaneously determining a mathematic relation between an oil-soluble ageing product (the content of furfuraldehyde in the oil) and an ageing state (the polymerization rate of the insulating paper) of the solid insulation and the like.