Abstract: The tarsometatarsus is an important component of the avian hindlimb. It is well known that the morphology of avian tarsometatarsus is a useful indicator of the locomotion and habit of a bird. This paper focuses on the morphology of the distal tarsometatarsus of birds. The tarsometatarsi of 154 specimens of living birds belonging to 15 orders were measured although over 200 specimens were examined. Statistic analysis of the morphology of the distal tarsometatarsus of extant birds was conducted. Correlation analysis and factor analysis indicated that two principal components were derived with each comprising 3 variables. The first principal component include the width of metatarsal trochlea II, III and IV; and the second principal component includes the relative height and anterior projection of metatarsal trochlea II compared to that of III, and relative anterior projection of metatarsal trochlea IV compared to that of III. Statistic analysis of these 6 variables showed that they could be used to well distinguish arboreal and terrestrial birds. In this paper, 4 variables of the distal tarsometatarsus were also collected from 25 specimens of fossil birds belonging to 14 genera of Early Cretaceous birds from Western Liaoning in China. Analyses of these variables have also proven to be useful in distinguishing arboreal and terrestrial birds, and the result is generally consistent with a conclusion reached on the basis of other analysis, i.e. those based on the claw geometry and toe proportion.