This paper researches the electrons horizontal vibration when the electrons have high velocity. Its experimental method is using the characteristics that β-particles of 90Sr source in different magnetic fields by half circle-focus β- spectrum and in the same radius have different energy and momentum to study the functional relationship between the particle number (n) and the width of the copper narrow slot (δ) when the particles fly across the copper narrow slots with different widths (thickness is 8 mm)and find that the β-particles have the horizontal movement tendency no matter what energy and momentum the β-particles have, and when they fly across the copper narrow step there is the distribution of a flight of steps. The reason may be that β-particles have the horizontal amplitude A and the interaction of energy fluctuation in vacuum.