The nano-crystalline CuCr25 alloys have been prepared and the breakdown experiments have been done in vacuum room. The traces of cathode spots on the surface of coarse-crystalline and nano-crystalline CuCr25 alloys have been observed using a scanning electron microscope (SEM). Experimental results show that the spot diffusion of coarse-crystalline CuCr25 cathode local iterative combustion or whole jumping move on the Cr phases with a weak voltage withstanding. But the spot diffusion of nanocrystallization of CuCr25 cathode exhibits quasi-continuous move, as one falls and another rises, due to the superior condition for electron emission, and the breakdown phase distributing on the whole cathode surface.