AbstractFor preserving global biodiversity, we should evaluate the level of endangerment of a species based on information such as number and distribution of individuals, fluctuations and decline in abundance and distribution, and risk of extinction.  We should then design conservation measures accordingly. The Species Survival Commission of IUCN has devoted itself to the study of IUCN Red List Criteria. The IUCN 40th Council Meeting adopted the so-called modified Mace Lande Endangered Species Criteria as the standard criteria for the IUCN Red List in November 1994. The Red List is intended to focus national and local conservation actions on the species that most need support. Although the IUCN Red List is not an international law, it has deep impact on conservation decision-making in governmental and nongovernmental organizations, as well as on conservation law and policy-making in many countries. The IUCN Red List Criteria also have had a profound influence on the theory of conservation biology. However, when we tried to apply the IUCN Red List Criteria to assess the status of endangered aquatic wildlife in China, we found several problems: (1) How do we distinguish those species that are naturally rare and those species whose population and habitat are declining due to human activity? (2) Can we apply the same criteria to different taxonomic groups, particularly those with different life histories? (3) How do we evaluate changes in population density that occur in the core habitat versus those that occur in peripheral habitats of the same species? (4) How should we treat the extirpation of local populations in a metapopulation? (5) How to deal with those species that can be successfully bred in captivity? (6) If we do not have accurate historical and current population and habitat status data, how do we evaluate the level of endangerment of those species? We suggest solutions to those problems in this paper. Firstly, we set up simplified endangered species criteria categories: “Least concern”, “Concern”, “Threatened”, “Endangered” and “Extinct”, of which, “Concern”, “Threatened”, and “Endangered” are further divided into two levels: “ordinary” and “highly”. We further suggest distinguishing ecologically endangered species versus evolutionarily endangered species, and evaluating species with different life histories, for examples, the K-strategists and r-strategists, with different criteria. Third, we suggest the introduction of “Economically Endangered” as a criterion of “Threatened” for r-strategy species. Fourth, more conservation attention should be allocated to endemic species. Finally, we introduce the metapopulation concept into evaluation of endangered aquatic wildlife.