Abstract:The identification of the photosynthetic pathway of 46 species from the Poaceae, Cypcraceae, Amaranthaceae and Asclepiadaceae were made using stable carbon isotope ratio measurements. 36 species showed the δ13C value of -10.43 to -13.66‰ and 1 species with succulent leaves had aδ13C value of -15.24‰. It is suggested that these species are new C4 and CAM type plants, respectively.According to the mean δ13C value of three C4 suhtypes proposed hy Hatteraley, it is possible that 8 species with δ13C value of -10.4 to -10.9‰ are NADP-ME type, and 6 species with δ13C value of-13‰ may be the NAD-ME type. The others will be NADP-ME or PCK type.