The fall webworm, Hyphantria cunea (Drury), is a quarantine pest native to North America that may be found worldwide. It has posed a serious threat to the ecological security of China since it was discovered in 1979. In recent years, with global climate warming, the H. cunea epidemic has spread south and voltinism has changed in some areas. To further explore the changes in the biological characteristics of H. cunea in different regions, the occurrence and diffusion process of H. cunea since its invasion in China was comprehensively analyzed. This analysis was based on 1979—2021 nationwide monitoring and census results, combined with the temperature change data in some regions. The reasons for the increase in the annual generation numbers in some areas are also discussed. In light of the evolution of the annual generation numbers and repeated outbreaks of H. cunea, several key issues that should be presently addressed are proposed. These include the significant increase in the expansion rate caused by the increase in the annual generation numbers, the relationship between the expansion potential and reducing the spread along the Yangtze River, the occurrence of outbreaks, and the lack of clear localization trends. With the increased requirements for invasive species management and the problems faced in the control of H. cunea in recent years, countermeasures and suggestions have been proposed. These include formulating prevention and control strategies under the premise of protecting the national biosafety bottom line, achieving control objectives under the overall planning of biodiversity protection, determining the rules of outbreaks and disasters under emergency preparedness, and improving the efficiency of epidemic identification to strengthen quarantine management.