In this study, we chose the withered litters of Cyperus malaccensis in Min River estuary wetlands as the research object, adopting different salinity (0,5,10,15) and flooding degree (unimmersed litterbags, flooded treatment Ⅰ and continuous immersion litterbag, flooded treatment Ⅱ) to do experiments on decomposition of the withered litters, of which its dissolved organic matter (DOM) content and structures of UV-visible spectroscopy, Fluorescence Spectroscopy, and Infrared Spectroscopy with changes in characteristics and so on. The results of this study show that the concentrations of dissolved organic carbon (DOC), total soluble nitrogen (DTN), dissolved inorganic nitrogen (DIN) and soluble organic nitrogen (DON) are of significant difference under the condition of different salinity and flooded treatment in the decomposition time (P<0.05) over 181 days of decay period. The concentrations of DOC and DON were no significant difference in different salinities, but the DIN in high salt group was significantly lower (P<0.05). The aromaticity index (AI) with different salinity treatments increased throughout the decomposition time except under the condition of flooded treatment Ⅰ. Different decomposition phases had important effects on the DOM components of C.malaccensis litters and spectral characteristics. At the earlier stage of decomposition (before 89 d), under the condition flooded Ⅰ, humification index of withered litters and debris (HIX_syn, HIX_em) was decreased when the salinity was increased. During the middle and later periods of litters decomposition (after 120 d), the higher salinity was in favor of the accumulation of humus. While under the condition of flooded treatment Ⅱ, the decomposition of litters was inhibited throughout the whole experiment period and thus the degree of humus was much higher. Water conditions also had an impact on leaching and humification of DOM of litter. The value of AI and HIX_syn were both higher in flooded Ⅰ treatments compared to flooded Ⅱ treatments at the earlier stage of litter decomposition, but more leaching of nitrogen was observed in the DOM of C. malaccensis litter under the flooded Ⅱ treatments than the flooded Ⅰ treatments in this phase. Humus and aromatic of the withered litters DOM were restrained due to the anaerobic environment under the flooded treatment Ⅱ condition during the middle and later periods of litters decomposition. Infrared Spectroscopy analysis indicates that the withered litters DOM of C. malaccensis in Min River estuary, of which the structure was simple and easy to resolve carbohydrates content which is comparatively higher. However, the structure characteristics of the withered litters DOM in C. malaccensis were unchanged under the two flooded treatments conditions.