Abstract. Sea-surface microlayer (SML) is the boundary interface between the atmosphere and ocean, exhibiting an enrichment of dissolved organic matter (DOM) and participating in air-sea gas exchange. However, how do DOM enrichment in the SML control the flux of several gases remains poorly understood. In our study, laboratory experiments and in situ investigation in the eastern marginal seas of China were conducted to determine the enrichment factors (EFs) of carbon monoxide (CO) and DOM and their production and consumption rates in the SML during winter. CO, chromophoric DOM (CDOM), and fluorescent DOM (FDOM) were frequently enriched in the SML during winter. Although CO, CDOM and FDOM concentrations decreased from in-shore regions to open ocean, higher EFs of CO and DOM in the SML were generally observed in off-shore regions. Moreover, the EF of CO was lower than EFs of CDOM and FDOM, which appeared to be related to the faster consumption rates of CO in the SML. Considering the photoproduction rate (mean value: 12.4 nmol L^-1 d^-1) was significantly higher than the bacteria consumption rate (mean value: 3.8 nmol L^-1 d^-1) of CO in the SML, the EF and the concentration of CO in SML showed a large diurnal variation, with the higher values observed in the early afternoon. The Flux of CO exhibited a significantly negative correlation with CDOM absorption (a_CDOM(254)) and fluorescence marine humic-like Component 3 in the SML, suggesting that elevated DOM could stimulate the photoproduction of CO, but may also decrease air-sea CO exchange in the SML.