We measured methane transport capacity and methane emission from Spartina alterniflora using the “hanging” enclosed static chamber technique and gas chromatography during neap tide from May 2009 to January 2010 in an S. alterniflora marsh in the Min River estuary. The main parts of methane release from S. alterniflora were also determined. Based on the above measurements we analyzed the contribution rate of plant methane transport to methane emission from the S. alterniflora marsh and measured methane concentrations in the medullary cavity of S. alterniflora. The methane transport capacities of S. alterniflora significantly differed during different growth stages, with the highest transport capacity in the fast growth stage. The contribution rates of plant-mediated methane transport to total methane emission from the S. alterniflora marsh ranged from 9% to 94%. Methane transported by S. alterniflora plant was mainly released at plant height 0 to 20 cm above ground, with the average contribution rate of this part to whole plant transport capacity being 50%. The methane concentration in the medullary cavity of S. alterniflora was much higher than that in the atmosphere and decreased from the bottom to the top of S. alterniflora plants.