Intensification of human activities is pushing our use of ecosystems beyond thresholds of resiliency. Given the accelerating global crisis of ecological sustainability, there has been enormous growth in research related to ecological security. However, differences in opinions on ecological security have hindered understanding and effective applications of this concept. To understand the development of research on ecological security, we reviewed its achievements and limitations over the past 30 years from three dimensions: definition, evaluation method, and approach to identify measures to improve the ecological security level. We used the Web of Science search engine to retrieve peer-reviewed journal articles published from 1990 to 2021 containing the keywords “ecological security” or “ecological safety”. There are three main ethical perspectives among the definitions of ecological security: nature-centric, human-centric, and eclectic; the human-centric view, which focuses on human well-being, is predominant in the field. Most studies employed the following three evaluation methods: quantitative comparison, composite indicators, and spatial analysis. However, the results of ecological security analyses were difficult to compare. Three main approaches (causality, correlation, and landscape) were used to identify the drivers of ecological security and propose measures for ensuring or improving ecological security. Owing to the complexity and heterogeneity of ecosystems, universally effective measures to ensure ecological security rarely exist. For the definition and evaluation of ecological security, a broader, non-anthropocentric perspective that incorporates the intrinsic value of non-humans in the context of cost–benefit, security–efficiency evaluations is essential. When proposing evaluation methods, the comparability of evaluation results should be given priority. To improve ecological security level, identifying the key drivers and/or potential optimal patterns of ecological security may be a promising solution.