The formation, wetting and spreading process of the liquid amorphous filler metal were investigated. The results indicate that the eutectic phase of the amorphous filler metal is damaged and plenty of high melting-point copper solid solution and copper-nickel compound are generated due to the full solid-phase diffusion before melting. Therefore, relatively less liquid phase is produced by amorphous filler metal than crystalline filler metal and the liquid phase spreading and flow is weak. However, the crystalline filler metal generates a large amount of liquid phase. Spreading and flowing of the liquid phase is the main process of crystalline filler metal brazing. As the amorphous filler metal is very thin, the atomic diffusion distance is very short in the filler metal, which is quite favorable for the rapid dissolution into the base metals. The ordinary filler metal is relatively thick, and it tends to take longer time to dissolve than the amorphous filler metal. The thickness of the residual filler metal decreases with the increase of brazing temperature and dwell time. The thickness of the residual layer of amorphous filler metal is smaller than that of the crystalline filler metal under the same brazing temperature and dwell time.