The equilibrium geometries and electronic structure properties of mixed Aun Xm(n+m=4, X=Cu, Al, Y) have been obtained by using the B3LYP hybrid wh ich is based on non-local density functional theory method. The binding energies, ionization potential, electron affinity, the highest occupied molecular orbital ener gy level, lowest unoccupied molecular orbital energy level,and the energy gaps o f them have been calculated. By analyzing the properties of electrons using the Mulliken population method, it is concluded that impurity increases the stabilit ies of Au cluster. When Cu, Al and Y doped in Au4 cluster, the energy gaps reduce and the binding energies increase.