Hainan Eld’s deer (Cervus eldi hainanus) was once widely distributed in Hainan Island of China. With the rapid increase of human population and the fast expansion of agriculture in the recent 350 years of Chinese history, the habitat of the deer has been greatly reduced. Habitat loss and hunting have driven the deer to the verge of extinction. The last group of 26 deer was protected at Datian Nature Reserve (DNR) which was founded in 1976. The habitat at present remains only 13.14 km2 at DNR, just 4.38–6.57% of that of the 1950’s. The deer population increased to over 1,000 individuals in 2003 under the protection of enclosure building along the boundary of DNR. Moreover, an off-site conservation approach for the deer has been launched since 1990. A total of 83 deer from DNR had been accumulatively introduced to establish off-site populations by the end of 2000. The off-site conserved populations had reached 263 by the end of 2002, of which 246 animals were born in captivity or semi-captivity. A new off-site population in the natural environment was founded by introducing 65 animals from DNR during July to December 2003. The deer population still however faces challenges of habitat limitation, decrease of genetic diversity, inbreeding and poaching. Conservation approaches needed to practice immediately have been proposed in this paper.