Abstract: In this paper, based on the feature of crystal sites occupied by alloying elements, a model cluster, investigating the interacting mechanisms of nonmagnetic element Cu in RECo₅ type alloy, has been presented. The electronic structure has been calculated with SCF-X-SW method. The calculating results show that, after Cu replaces 2c crystal site Co, the energy spectrum of the model cluster will move towards shallow well potential, energy gap will become small, the charge a momg the atoms will be redistributed, and some new stales to which impurity contributes will be produced; Partial-wave local density of slates gave interactions between atoms. Results of Hellmman-Feynman force show that thermal expansion anisotropy of the model cluster will be decreased considerably after Cu insteads of 2c crystal site Co.