Single-helical or double-helical structures are common in all living organisms, such as RNA and DNA. Helical assembly has been found in the artificial nanoparticles, but how they do so remains poorly understood. Here, we exploit atomically precise Au6Cu6 alloy nanoparticles (or called nanoclusters) as building blocks to construct a single-helical Au12Cu12 superstructure in an operative path, thereby providing access to currently elusive mechanistic pathways. We propose that the thermodynamically viable linear-to-bent process at a couple of Au6Cu6 nanoclusters imparted by the organic ligands seems to be critical for the helical-nanostructured arrangement of Au12Cu12. This study could help to offer new design rules for the exquisitely helical structure assembled from nanoparticles.