Biological invasion is a complex and orderly dynamic process characterized by remarkable spatiotemporal heterogeneity of occurrence and harm. Such heterogeneity is usually determined by the interaction of natural, biological, and social factors in the system composed of origin, invasion place, and their connections. Network theory is a method to study complexity science and complex systems. Its essence lies in revealing the commonness of structural features behind the complex system, abstracting the rules and common features from complex information. In the past 20 years, network theory has been applied to the study of biological invasions. The objective of this study was to review the progress of the application of network theory in biological invasions, clarify the main research directions and hot topics, and provide new ideas and methods for the innovative research of biological invasions in China. Since 2000, the published studies on biological invasions using network theory mainly focused on assessing the risk of invasive species and the impact of invasive species on ecosystems. The risk assessment of invasive species in transcontinental transport networks, the effect of landscape connectivity on the dynamics of invasive species expansion and diffusion, and the impact of invasive species on the network of interactions between species in local ecosystems are the hot topics. Before 2013, published papers mainly focused on ecosystem impacts, and in the last ten years, it was primarily on risk assessment of alien species. Few studies have been carried out on network theory in China, and all concentrated on the ecological system damage. Future studies on the risk assessment of spatio-temporal quantitative introduction and spread of invasive alien species should be strengthened by using network theory and thus upgrade our managing ability for early monitoring and warning of a new invasion and prevent the introduction and spread of more invasive species.