Abstract: The development of the low-altitude economy in China faces a core challenge of the lack of established routes for low-altitude flights. Focusing on the characteristics and risks of low-altitude flights, this study aims to develop a digital air-route network scheme in the absence of matching low-altitude physical infrastructure. First, this study analyzed the characteristics of low-altitude airspace, including fragmentation, geometric complexity, and sensitivity to microscale meteorology; the characteristics of low-altitude flights, encompassing low altitudes, low flight speeds, and small radar cross-sections; and dual risks posed by both air and ground factors. Then, this study reviewed the current status of domestic and international studies on low-altitude air-route networks, as well as the development paths of associated policies and practices. Accordingly, this study clarified the connotations of the digital air-route network and distilled the scientific problems concerning the fine-scale detection of geographic information, the prediction of high-dynamic stress information, and quantitative risk assessment. Furthermore, this study summarized key technologies for risk quantification, topological construction, and the calculation of navigation attributes and developed a low-altitude navigation architecture and service model based on the digital air-route network. Finally, this study presented relevant technical cases and validation results of the digital air-route network. This study provides both fundamental navigation for low-altitude flights and a methodological basis for low-altitude infrastructure planning and fine-scale airspace management, contributing to the high-quality development of the low-altitude economy.