More than 1700 C₄ plant species have been identified over the world wide since the work of Downton and Tregunna (1968). Most of these studies focused on the classification of plant species as to their photosynthetic pathway types (C₃, C₄ and CAM), geographic distribution of C₄ plants and their relationships with climatic patterns. But very few have exami the relations between C4 species and vegetation dynamics, especially in agro-pastoral ecotones. By dint of morphological functional types, C₄ plants and their relations with habitats in agro-pastoral ecotone North to the Beijing were analyzed based on field survey and references. Of the total identified 733 species in 304 genera and 66 families, only 64 species in 40 genera and7 families were found with C₄ photosynthesis. This indicated that the C₄ species mainly occurred in a few families in the region, but most of these species were common species and related with vegetation dynamics. Gramineae is the leading family with C₄ photosynthesis (43 species), Cyperaceae ranks the second (16 species), then followed by Chenopodiaceae (5 species). The significant increase of C4 species in the communities with land deterioration suggested C₄ plants remarkably response to the land-use frequency and intensity in the ecotone. The number of C₄ species and proportion of C4/total increased with desertification from RL to DC. The total number of C₄ species dropped significantly from RL to SS and SL, while proportions of C₄ species increased significantly. For each morphological functional types, C₄ proportion in ANG was much high (64%), followed by SPG (53%), HPG (18%), ANF (14%), but that in SHR and PEF were much lower (less than 1%). The proportions of ANG and ANF in DC, WE, SS and SL habitats exceeded by 50% respectively, and 30% in RL, indicating that communities were not stable in this ecotone. The findings suggest that the photosynthetic pathways, combined with morphological functional types, are efficient indications for studying the linkage between species and habitats in the region.