In the foreseeable future, the further civilian and mass utilization of unmanned aerial vehicles (UAVs) underscores the critical significance of researching UAV operational risks to ensure their safety. Currently, most UAV risk studies rely on traditional risk assessment methods, often evaluating operational risks based on singular or a few indicators. This study takes a comprehensive approach by considering various indicators related to UAV operational safety. It establishes a comprehensive indicator system that addresses aspects such as operational safety, reliability, and public acceptance. The study also provides both quantitative and qualitative risk assessment methods for these indicators. Additionally, the integration of a risk map offers a novel visualization technique for assessing UAV operational risks. This integrated approach aims to provide a secure foundation for the extensive future operation of UAVs in urban low-altitude airspace.