Abstract: Conventional paraffin sectioning was used to observe the crosscutting structure of Spartina alterniflora roots grown under different salinities. To examine the plant's adaptability to salty environments, the characteristics and changes in root structure were compared along with changes in salinity. Results showed the following: (1) The roots of S. alterniflora were of primary structure; (2) The epidermal cells of the mature roots were destroyed and mostly fell off, while the exodermis and cortex aerenchyma were well-developed; (3) The endodermis cell walls thickened obviously in five surfaces, increasing at first and then decreasing; (4) The central vascular cylinder was filled with mechanical tissues, and the pericycle cell walls were also thickened. The structural characteristics of these roots showed the adaptation of S. alterniflora to salty environments.