Abstract: The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis; YFP) is now critically endangered, calling for prompt and effective actions to strengthen research and conservation. The Poyang Lake is the most critical habitat of the YFP, holding almost half of the whole wild population of this species. And thus, this population is vital for the conservation of this critically endangered species. In this study, to evaluate the genetic diversity of the porpoise population living in the Poyang Lake and to predict its development in the future, both blood samples from live YFPs (124 individuals) and tissue samples from 42 stranded YFPs have been analyzed by using 10 microsatellite genetic markers. Results indicated that the Poyang Lake porpoise population has a moderate level of genetic diversity, with an average allele number of 5.80, an average observed heterozygosity (H_o) of 0.653, and an expected heterozygosity (H_e) of 0.664. Meanwhile, when samples from stranded porpoises were excluded, the mean number of alleles decreased to 5.50; three unique and rare alleles at three microsatellite loci were found exclusively among stranded porpoises, indicating that abnormal deaths caused by anthropogenic reasons might lead to genetic diversity loss of this population in the Poyang Lake. Besides, the software BottleSim V2.6 was applied to simulate the developing process of genetic diversity in this population. Simulations results showed that genetic diversity would decline quickly if kept its current effective population size (N_e=62) and sex ratio (0.87﹕1); while an effective population size of more than 200 individuals or a census population size of more than 1000 individuals is necessary, to realize the long-term goal of preserving more than 90% genetic diversity in 100 years. Results obtained in this study are significant for the genetic conservation of the population living in the Poyang Lake, and the whole species as well.