Syndecans are single-span membrane proteins playing important roles in cell-cell and cell-matrix interactions. The transmembrane domain of syndecans is critical for signal transduction across the cell membrane. Here， the structure of the transmembrane domain of syndecan-2 in detergent micelles was investigated using solution NMR spectroscopy. Backbone resonance assignment was obtained， and NMR studies show that the transmembrane domain forms a helix in detergent micelles， which is also supported by the hydrogen and deuterium exchange experiment. A study of the dynamics revealed the rigid structure of the transmembrane domain formed in solution， and paramagnetic relaxation enhancement defined the topology of the transmembrane domain in detergent micelles. This structural analysis may facilitate a better understanding of the role of the syndecan-2 transmembrane domain in signal transduction.