Eleocharis baldwinii is a freshwater amphibious plant belonging to Cyperaceae.It can adapt and grow well in the submerged and terrestrial conditions.In this study,the photosynthetic characteristics of E. baldwinii in the submerged and terrestrial conditions were investigated.The results of anatomical section,enzymatic activity of major enzymes in C4 cycle and stable carbon isotope analysis showed that the photosynthetic pattern was C4 in terrestrial condition and C3-C4 intermediate in the submerged condition.The chromosome number is 20 based on chromosome tableting.It will lay a foundation for the reverse genetics and the genome sequencing of E. baldwinii.