Abstract: Based on the formula of range and that of real efficient secondary electron yield from metal, the relation among energy exponent, incident energy and the real efficient secondary electron yield at high incident electron energy was derived. Based on the relation between the real efficient secondary electron yield and secondary electron yield at high incident electron energy of metal, the relation among the energy exponent, incident energy and the secondary electron yield at high incident electron energy was derived. The energy exponents (n) of the primary electrons hitting on gold and silver is computed with experimental results. The experimental results also validate the relation among the incident energy,energy exponent and the secondary electron yield at high incident electron energy for