An investigation was performed to reveal the relation between production and decomposition of the Miscanthus sinensis and Arundinella hirta grasslands in Mt. Kwanak. 1. The total annual litter productions of M. sinensis grassland A, B and A, hirta grassland were 2,267.12, 943.44 and 1,228.45 g/m$^{2}$, respectively. 2. The decay constants of litters of M. sinensis grassland A, B and A. hirta grassland were 0.732, 0.411 and 0.877. 3. The time required for the decomposition of half of the accumulated organic matter of M. sinensis A,B and 4. hirta were 0.9, 1.7 and 0.8 years, for 95% of elimination 4.1, 7.3 and 3.4 years, and for 99% of elimination 6.8, 12.2 and 5.7 years respectively. 4. The decomposition rate of grass litters was affected by the soil water content and grass species.