At present, most freshwater lakes in China are severely polluted and degraded. In this regard, we have achieved considerable initial success using a number of restoration techniques. There are many factors that affect the degradation of freshwater lake ecosystems, including both biotic and abiotic factors. These factors are interrelated and interact with each other, and thus causal mechanisms are complicated. In this paper, we initially introduce the meaning and degenerate forms of freshwater lake ecosystem degradation. We then summarize the factors driving the degradation of freshwater lake ecosystems. From the perspectives of ecological integrity and degradation restoration techniques, freshwater lake ecosystems are mainly affected by three types of driving factors (physical, chemical, and biological), which essentially follow the "environmental change-driving force-pressure (threshold)-state-response" principle. We then construct a technical system for a freshwater lake ecosystem restoration module, based on functional modules of freshwater lake ecological systems and practical experience of lake ecosystem restoration, to clarify the driving principle of lake ecosystem degradation, and subsequently discuss and compare degenerate restoration techniques in water eutrophication and freshwater lakeside wetland ecosystems. Finally, we present an outlook of the long-effect mechanism of remediation technology, and the future mechanisms of action and pathways of the driving factors of environmental change in freshwater lake ecological restoration.