Many researchers have documented that rice-mediated transport is the major pathway potentially accounting for more than 90% of the total CH4 emitted from soils over the growing season. However, characterization of the individual CH4 transport like ebullition as gas bubbles and rice plant has not been well elucidated in green-manure amended mono-rice paddy soil. A mixture of barley (75% of the recommended dose, RD), and hairy vetch (hereafter, vetch, 25% of the RD) seeds were broadcasted after riceharvesting in the experimental farm of Gyeongsang National University (36o 50` N and 128o 26` E), Jinju, South Korea, and the above-ground biomass (34-36 Mg ha-1 with 67-69 % moisture content) were harvested before rice transplanting in 2011 and 2012. The fresh biomass was chopped in a 5-10 cm length and incorporated with different ratios (0-100%) one week before ricetransplanting under the same chemical fertilization (N-P2O5-K2O= 90-45-58 kg ha-1). The combination of cover crop biomass was applied at the rate of 0, 9, 18, 27 and 36 Mg ha-1 on fresh weight basis to investigate their effect on CH4 emission through direct ebullition from the soil and rice-mediated transport during rice cultivation. With increasing biomass application, the plant-mediated CH4 transport sharply increased until the vegetative stage of the plant, while CH4 emission through direct ebullition from soil was higher at the reproductive stage of the plant than plant-mediated transportation. Our result predicts that ca. 9 and 91% of CH4 emitted through plant-mediated transport and direct ebullition, respectively in paddy soil applied with green manure applications. Incorporation of cover crop biomass at 9 Mg ha-1 was optimum for the reduction of CH4 emissions in soil and its increased application can significantly increases CH4 emission during rice cultivation.