Methane (CH_4) is an important greenhouse gas in the atmosphere and contributes 15% to global warming. Coastal wetlands, one of the important intertidal ecosystems at the land- ocean interface, are considered a large potential natural source of CH_4. In this paper, the study dynamics of CH_4 production process, CH_4 flux characteristic and affecting factors are summarized. The study of CH_4 production processes is mainly based on molecular biology, with much research in freshwater wetlands. The CH_4 flux characteristics in coastal wetlands has distinct temporal-spatial variation affected by many factors, such as soil physical and chemical properties, hydrological conditions and plant communities. The hydrological condition is a determining factor for the production and emission of CH_4, effects of temperature and pH on CH_4 emissions by affecting the methanogenic activity. Research on the effect of salinity on CH_4 of coastal wetlands has mainly focused on concentration, and the study of composition of SO_4~(2-) plasma in salt is not deep. The transmission of plants is the basis for the study of CH_4 emission dynamics, and there are many studies on the effects of plant species and density on CH_4 emissions. With human activities and environmental pressure, there is a great influence on coastal wetlands CH_4 emissions. CH_4 emissions from coastal wetlands are affected by many factors, and the process is complicated. Aspects to strengthen in the future include the effects of soil physical and chemical properties on CH_4 emission, especially the effect of ion composition and concentration in salt on CH_4 emissions; the effects of plants on CH_4 emissions;the effects of human activities on CH_4 emissions;and evaluation of CH_4 flux at long time scales and across large spaces.