Abstract: Using morphometry of ungulate pellets to determine sex and age is the preferred method in field studies on ecological differences between two sexes, especially sexual segregation of ungulates. This study examined the morphometry of 4,006 pellets from ≤145 Eld’s Deer (Cervus eldi hainanus) collected in Hainan Datian National Nature Reserve in March 2006. The deer were divided into five sex-age categories as adult male, adult female, sub-adult male, sub-adult female, and calf. They were analyzed using four direct measurement indices (dry weight, length, width, and volume) and two indirect indices (length-to-width ratio, and ellipsoid-shape index) by use of step-wise discriminant and fuzzy cluster analyses. Discriminant analysis could correctly distinguish 76.17% of adult males, 42.22% of adult females, 34.94% of sub-adult males, 40.46% of sub-adult females, and 79.34% of calves. Fuzzy clustering analysis enabled to correctly distinguish 19.48% of adult males, 20.02% of adult females, 37.37% of sub-adult males, 42.82% of sub-adult females, and 91.50% of calves. Therefore, it is more credible to determine calves and secondarily adult males by use of pellet morphometry. We advise that pellet morphometry should be used for determining sex and age categories in surveys at the population level rather than at the individual level.