Population viability analysis is a method of evaluating population size and extinction risk of threatened species, through analysis of factors such as population statistical randomness, environmental randomness, natural disasters, spatial structure of habitats and various management approaches to assess their impacts on threatened species and provide theoretical support for conservation and management strategies.The Père David’s deer (*Elaphurus davidianus*) population in the Dongting Lake is a naturalized population. Due to low population growth as a result of flooding, and the threat of insularization and inbreeding depression, it is necessary to formulate a conservation action plan to preserve that population. We monitored the population from 2006 to 2020 and analyzed population viability based on the data collected. There were 3 groups of individuals in the area, with a total population size of about 210 individuals. We used the VORTEX model (10.5.5.0) to simulate dynamics of the population for the next 100 years based on various population parameters, including current population status, mating system, carrying capacity, and mortality. Under ideal conditions and assumed carrying capacity of 1 000 individuals, the probability of population extinction is 0, the intrinsic growth rate *r* is 0.0991 ± 0.0800, the instantaneous growth rate *λ* is 1.1041 ± 1.1900, the net reproduction rate *R*_{0}* _{}* is 2.006 2, the average generation time of females