Abstract: The surface-distribution and line-distribution of W element in SiC/W diffusion couple were analyzed under 10 kV and 20 kV accelerating voltage by using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that the overlap between the M spectrum series of W element and K spectrum series of Si element occurred in that there was only the M spectrum series of W inspired under 10 kV accelerating voltage. Obviously, it was the reason that it is difficult to distinguish between W and Si elements through surface-distribution and line-distribution in SiC/W diffusion couple. When the accelerating voltage was increased from 10 kV to 20 kV, the distribution of W element is characterized by inspired the L spectrum series of W element, which made the distribution of W element close to the real distribution. The EDS data further confirmed that the disordered distribution of the W element under the 10 kV accelerated voltage was caused by the overlap between the M spectrum series of W element and the K spectrum series of Si element.