Using density functional theory calculations, we compared four kinds of possible structural motifs of the medium-sized Au-n (n = 21-28) clusters, i.e., fcc-like, double-layered flat, tubular cage, and close-packed. Our results show strong competition between those structural motifs in the medium-sized gold clusters. Au-n (n = 21-23) adopt fcc-like structure owing to the high stability of tetrahedral Au-20. A structural transition from fcc-like to tubular occurs at Au-24, and the tubular motif continues at Au-27 and Au-28. Meanwhile, a double-layered flat structure was found at Au-25, and a pyramid-based structure at Au-26. The relationship between electronic properties and cluster geometry was also discussed.