The methane emission out of seabed could seriously affect Earth’s climate and is usually associated with the dissociation of the gas hydrates stored in marine sediments on the continental margins. Spatially, the gas emission out of seafloor is not evenly distributed in continental margins. Gas emits out of seabed generally through submarine mud volcanoes and gas seeps. To understand the seabed gas emissions off SW Taiwan, we investigate the distributions of the submarine active mud volcanoes, gas seeps and gas plumes off SW Taiwan. We examine all the available sub-bottom profiler and EK echo sounder data. In total, we have identified 19 submarine mud volcanoes, 220 gas seeps and 295 gas plumes. The gas emissions are generally distributed at the crests of mud diapiric ridges. Particularly, most of the active mud volcanoes and gas seeps cluster at the KASMVG (Kaoping submarine mud volcanoes group) area. We speculate that the intensive mud volcanism and gas seepage at the KASMVG area are ascribed to the erosion of the submarine channel along the base of the continental slope. The erosion has caused a deep V-shaped channel and a steep slope of the BSR (Bottom-Simulating Reflector) curve across the continental margin. The upward migration rate of free gas beneath the BSR is thus increased and has intensified mud volcanism and gas seepage at the KASMVG area. The gas seeps can reduce the slope stability and generate small-scale slides. Whereas, the well development of the mud volcanoes in an area could effectively disturb the seabed morphology so that a large-scale submarine landslide cannot easily happen.