Abstract: Abstract: Methane (CH4) is the second most important greenhouse gas, after Carbon Dioxide (CO2). The concentration of CH4 in the atmosphere is still rising more rapidly than ever before. Among them, most CH4 sinks are widely distributed in water-unsaturated lands. It is a high demand to clarify the CH4 uptake characteristics in the different types of soils in response to certain environmental factors. The soil CH4 uptake potential can then be improved to mitigate global warming. In this study, a soil laboratory incubation experiment was conducted to investigate the CH4 uptake rates of the salt-affected soil at the different moisture (50%, 75%, and 100% of Field Capacity (FC)), and Salinity Levels (LS1: 0.3 dS/m, LS2: 1.0 dS/m, LS3: 2.0 dS/m, LS4: 3.2 dS/m, and LS5: 4.9 dS/m, and LS6: 6.2 dS/m). A field plot experiment was also carried out to verify the reproducibility of the laboratory incubation under natural conditions. The soil CH4 uptake was characterized by three soil salinity levels (PS1: 0.3 dS/m, PS2: 1.0 dS/m, and PS3: 5.0 dS/m), and their responses to the soil moisture dynamics. The soil laboratory incubation results showed that the cumulative CH4 uptake of soils (including all six salinity levels) under 100%FC was 1.08-1.39 times those of the 75%FC, and 1.27-1.72 times those of the 50%FC, respectively. It infers that the capacity of soil CH4 uptake increased with the increase of soil moisture within the range of field water-holding capacity. By contrast, the cumulative soil CH4 uptake decreased under all three soil moisture levels, as the soil salinity increased from 0.3 to 6.2 dS/m. Specifically, the cumulative CH4 uptake of the highest salinity LS6 was significantly reduced by 42.6%, 52.3%, and 55.1% under three soil moisture levels, respectively, compared with the non-saline soil of LS1. The soil moisture with the 100%FC aggravated the soil CH4 uptake capacity along the salinity gradient from 0.3 to 6.2 dS/m, compared with the 50%FC. There was a significant interaction between the soil moisture and salinity on the soil CH4 uptake. The laboratory incubation was validated by the field plot experiment under natural environments. The soil CH4 uptake rates were significantly positively correlated with the soil moisture for all three soil salinity levels (P<0.01). Compared with soil PS1, both PS2 and PS3 salinity levels led to a significant decrease in the cumulative CH4 uptake, indicating that the high salinity significantly inhibited the soil CH4 uptake. The laboratory incubation and field experiments indicated that the salt-affected soil was a CH4 sink, where the CH4 uptake capacity depended mainly on the soil moisture and salinity. Consequently, a sub-goal of the water-salt regulation can be formulated to improve the CH4 sink capacity for the high agricultural productivity in salt-affected soils.