Abstract: When measuring the wall thickness of a component with a cladding layer by pulsed eddy current testing(transient electromagnetic method) technology, the aluminum sheet has some influence on the PEC signal. The late signal slope of the straight line in the mono-logarithmic coordinate system was used as the characteristic value of the wall thickness measurement. The fitting relationship between the wall thickness and the characteristic value was obtained through the experimental data.The results show that the influence of aluminum sheet on the measurement results is closely related to the wall thickness of the component to be measured.The thinner the wall thickness is, the greater the influence is.When the wall thickness is greater than 6 mm, the influence of aluminum sheet is small. The thicker the aluminum sheet, the greater the influence on the thin-wall thickness of the measured component, the greater the measurement error.When the late signal slope is used as the characteristic value of the wall thickness, the lift-off has little effect on the measurement results.