Abstract: This paper studied the optimization of online and offline ET signal processing procedure in oxide layer measurement of fuel rods by utilization of median, interquartile range and on-site inspection experience. Online verification by the calibration signal combined with the oxide layer prediction curve are proposed to assess the effectiveness of the acquisition signal. By this way, the problem of handling fuel assembly frequently can be improved. In addition, it is found that the median statistics can avoid the interference of extreme signal compared with average statistics. And most of the average interquartile range of divided 150 mm parts of three fuel rods is between 0~   3 μm. The results indicate that the oxide layer thickness level of each part can be represented well by the median.