Abstract: Ionization potentials and electron affinities of Cux (n = 2-7) atomic clusters with the optimal geom etries have been calculated by use of SC F-Xa-SW method and Slater's transition state theory. Theo retical calcuIations show that the ionization potentiaIs and electron affinities of Cu. (n = 2-7) atom ic clusters have a sharp even / odd alternation with increasing their sizes, which are related to the electronic structure of Cun atomic clusters. The theoretical results are consistent with the related ex perimental ones.