Abstract: Only one wild population of the Crested Ibis (Nipponia nippon)survives by now, and its size has been no more than twenty since being rediscovered in 1981. We put forward the population dynamics and endangered level by Population Viability Analysis (PVA) with the help of a computer simulation model——VORTEX model on the basis of the data from 14 year long monitoring. The result indicated with probability of 98.5 % that the Crested Ibis would be extinct 50 years later. The mean extinction time is 15.72 years. The population is so small that the fate of this species is strongly influenced by demography stochasticity. Sensitive analysis showed that the survival probability was sensitive to catastrophes and environmental variations.Consequently, the prior conservation project is controlling hunting and predating, as well as artificial intervention on behalf of the birds to improve the survival rate.