Methane hydrate has been confirmed to be present in the South China Sea (SCS) based on drilling expeditions and geophysical indications. It is necessary to access the methane hydrate inventory because of its role in the energy resources and climate change. The aim of this study is to constrain the inventory of methane hydrates in the SCS formed by the microbial degradation of organic matter within the gas hydrate stability zone (GHSZ). Bathymetry, seafloor temperature, and geothermal gradient datasets enabled us to estimate the GHSZ at a resolution of 30 '' x 30 '' for the SCS. We conclude that the GHSZ occurs at water depths of > 500 m in most areas of the SCS. The methane hydrate distribution formed by microbial methane production in the SCS was computed using the parameterized transfer function recently proposed by Wallmann et al. (2012). The result indicates widespread accumulations of methane hydrate along the continental slopes in the SCS. The microbial methane hydrate is distributed over a 7.69 x 10(11) m(2) area and the total abundance of methane hydrate in the SCS is estimated to be 42.8 Gt C.