Abstract: Geothermal activity is an important form of earth degassing, which is frequently accompanied by a large number of greenhouse gas emissions. Taking Mapamyum of non-volcanic geothermal region in Xizang as a study case, the authors evaluated the degassing flux of geothermal soil CO₂ based on the Fick's law of diffusion. The results indicate that the soil CO₂ degassing flux is from 0.167 to 0.771 kg /(m²·a), while the fumarole CO₂ degassing flux is from 2.054 to 7.877 kg/(m²·a) which is 18.9 times that of the soil; Compared with global volcanic soil (0.001 ~ 2.25 Mt/(km²·a), the soil CO₂ degassing flux is significantly lower in value butlarger than the Alpine grassland ecosystem soil CO₂ emissions in the Xizang Plateau (187.46 g(m² a)^-1)). Combined with tectonic setting, the authors evidently hold that CO₂ in the geothermal system is mainly derived from magma degassing and hydrothermal fluid with walk rock alterations such as feldspathization. The low zone of soil CO₂ degassing flux is constrained by the poor permeability clastic sedimentary cover.