Nanotechnology is the engineering of functional structures at the molecular scale. In an era of dramatic changes, enterprises tend to rely on the tracking of the main trends of technological evolution as a way to maintain a competitive advantage. This paper explores the evolution of nanotechnology via an analysis of the patent citation network from the database at the United States Patent and Trademark Office. A total of 518 patents on nanotechnology were analyzed. The trend of nanotechnology and the patents of high betweenness centrality were identified. It was found that the technical classifications of “chemistry of inorganic compounds” and “semiconductor device manufacturing” have the highest potential for future growth. Since the 1980s, these classifications have had a stable number of filed patents and have become the mainstream of nanotechnology development. In addition, the present study also showed that the patents owned by the US account for a large portion of the applications in the main technical classifications which have played an important role in the evolution of nanotechnology. The results have shown that an analysis of the patent network can be a useful tool in both understanding and predicting the trend of an emerging technology. Keywords: Nanotechnology; Patent network; Technological evolution