Abstract: The electron beam in the electron beam welding machine has the characteristics of high-power density (10⁶−10⁸ W/cm²) and small focal spot size (several hundreds micrometers). Its beam density distribution is an important beam quality parameter and is of great significance to welding process research. However, traditional electron beam density measurement methods, such as fluorescence imaging, cannot be used at such high-power densities. We studied a measurement method based on a combination of a water-cooled Faraday cup with a micro aperture and high-frequency beam scanning. Adding a high-frequency (1−10 kHz) signal to the deflection coil of the electron beam welding machine causes the electron beam to scan within a larger size range, thereby reducing the power density of the electron beam deposited on the surface of the Faraday cup to avoid being burned. Water-cooled Faraday cups that can be used in vacuum chambers are specially designed to take away the heat deposited by the electron beam on the surface of the Faraday cup through water cooling. There is a micro aperture with a size of tens of micrometers on the surface of the Faraday cup. When the electron beam passes through the micro aperture periodically, a small amount of the electron beam passes through the aperture and enters the Faraday cup, forming an electrical signal that is amplified by an amplifier integrated in the Faraday cup and then collected. The electron beam power density distribution can be reconstructed from the collected current signal in the time domain. Experiments have shown that this method can accurately measure the density distribution of high power density electron beams in electron beam welding machines, while having an imaging accuracy of about 23 μm.