BACKGROUND: Gypsum($CaSO_4{cdot}2H_2O$) is known as an ideal amendment to improve soil quality of the reclaimed coastal land. Since gypsum has very high concentration of electron acceptor like ${SO_4}^{2-}$, its application might be effective on reducing $CH_4$ emission during rice cultivation, but its effect has not been studied well. METHODS AND RESULTS: The effect of gypsum on $CH_4$ emission and rice growth characteristics was studied by pot test, which was packed by reclaimed paddy soils collected from Galsa, Hadong, Gyeongnam province. Chemical-grade gypsum was applied in two soils having EC 2.25 and 9.48 dS/m at rates of 0, 0.5, 1.0 and 2.0%(wt/wt). $CH_4$ emission was characterized a week interval by closed chamber method during rice cultivation. $CH_4$ emission rate was significantly decreased with increasing salt accumulation and gypsum application levels. With increasing gypsum application, dissolved ${SO_4}^{2-}$ concentration in the leachate water was significantly increased, which might have suppressed $CH_4$ production in soil. Total $CH_4$ flux was dramatically decreased with increasing gypsum application. In contrast, rice yield was increased with increasing gypsum application and then achieved maximum productivity at 1.0% gypsum application in two soils. CONCLUSION(s): Gypsum is a very good soil amendment to suppress $CH_4$ emission in reclaimed coastal paddy soils, and improve rice productivity and soil properties. The optimum application level of gypsum is assumed at ca. 1% to improve soil productivity with reducing effectively $CH_4$ emission during rice cultivation.