Abstract: Both the mechanism of oxide film removal from metal surface and the brazing alloy spreading phenomena during vacuum brazing of nickelbase and ironbase alloys were studied in detail.Studies were performed utilizing a series of modern instruments such as Scanning Electron Microscope (SEM)、Energy Dispersive X-ray Spectroscopy (EDX)、X-ray Photoelectron Spectroscopy (ESCA),X-ray Fluorescence Spectroscopy (XRFS)、Quadropolc Mass Spectroscopy (QMS) and etc.Based on the analysises of physicochemical processes being observed on the metal surfaces and interface,the author deals with the mechanism of oxide film removal from nickelbase and ironbase alloy sufaces,and suggests some specific spreading patterns of brazing alloys.