Multiple-twinned gold nanostructures with decahedral shape have been prepared in aqueous solution by a one-step thermal process method. The decahedra of nano-gold can be obtained by heating aqueous PVP/HAuCl4 solution. In this process, poly(vinyl pyrrolidone) (PVP) acted as both reducing agent and shape-controlling surfactant. By control of the reaction condition, decahedral, icosahedral, and plate-like gold nanostructures have been obtained.