Abstract: Thiol-modified Spartina alterniflora (TMSA) was prepared via esterification with mercapto-acetic acid. Fourier transforms infrared (FTIR) was applied and confirmed that thiol groups were anchored onto the surface of Spartina alterniflora (SA). The TMSA was applied in the adsorption of cationic dye (methyl violet and methylene blue) in the synthetic wastewater. The results showed that the adsorption capacity decreased with the increase of the dosage of the adsorbent, and the proper pH value was around 8. Equilibrium sorption capacity increased with increasing the initial dye concentration or solution temperature (10-30 ℃). The adsorption kinetic data fit well with the pseudo-second-order model. The Langmuir isotherm model was found to fit well with the adsorption process.