The energetic and magnetic properties of the tubular cluster Au-24, doped endohedrally by a 3d transition-metal atom M (M = V, Cr, Mn, Fe, Co, and Ni) have been investigated by the scalar relativistic density functional simulations. It is found that (1) these 3d transition-metal atoms can be encapsulated stably into the tubular Au-24 and do not significantly perturb the atomic and electronic Structures of the parent tubular Au-24, (2) the infrared (IR) spectra of the tubular Au-24 Cluster are significantly changed by the dopant atoms, inducing a characteristic absorption peak in the IR spectra of all the M@Au-24, and (3) protected by the tubular Au-24, the 3d states of the dopant atoms are largely localized, and the atom-like magnetism is retained for all the doped gold Clusters, exhibiting 3, 6, 5, 4, 3, and 2 mu(B) for V-Ni, respectively.