The biological removal of CH 4 by methanotrophic (CH4-oxidizing) archaea always occurs at a distinct zone which is known as sulfate-methane transition zone (SMTZ). It is an important indication for high methane flux and gas hydrate occurrence. In this study, we collected pore-water data from South China Sea, Carolina Rise and Blake Ridge to analyze the relationship between CH 4, SO 4 2– concentration and depth. We found that below the SMTZ, the methane concentration increases continuously with depth and sulfate concentration decrease linearly to zero. In addition, the geochemical data taken from all these sites show that SMTZ is relatively shallow (less than 20 m), which may indicate that these areas have high methane flux.