Microplastics may play an important role in the migration of contaminants. Meanwhile, drastic changes in water salinity significantly impact adsorption or desorption. The present work investigated the adsorption and desorption of 2,4-dichlorophenol (2,4-DCP) on microplastics in different salinities which were simulated by river water (0.3 parts per thousand), lake water (15 parts per thousand, 35 parts per thousand and 70 parts per thousand) and sea water (15 parts per thousand, 35 parts per thousand and 70 parts per thousand), and was monitored by quartz crystal microbalance (QCM) and batch experiment. Furthermore, ATR-FTIR and Raman's analysis were performed for microplastics before and after adsorption in different water systems, which provided evidence of 2,4-DCP linkage on microplastics. The mass of 2,4-DCP adsorbed on the microplastics showed the highest in river water (0.92 mu g cm-2) and desorbed more and faster in 35 parts per thousand sea-salt water, which means that the most efficient adsorption was achieved in freshwater and slightly decreased in seawater. The influence of salinity on the adsorption of 2,4-DCP may be due to the electrical double layer, and ions from lake and sea salt may also compete for the adsorption sites on the surface of microplastics. The findings of this study will contribute to a deeper understanding of the fate of contaminants adsorbed on microplastics in arid regions and estuary environments, which are subject to rapid changes in salinity.