The use of green manure crops such as barley and hairy vetch is the most popular method for reducing chemical fertilizer application and maintaining soil fertility in Korea. The mixtures of legumes and non-legume can be an efficient tool to combine the benefit of the single species in the cover crop practice. However, there is a lack of information on how the species proportion may affect biomass production and N accumulation and how this can influence the subsequent rice production. In this study the effect of barley and hairy vetch grown in pure stands or in mixtures with different sowing proportion on biomass production and nitrogen accumulation was tested. All aboveground biomass of green manure was incorporated for rice cultivation before one week of rice planting. The standard sowing rates was 180kg ha?¹ for barley and 90kg ha?¹ for hairy vetch. The following seed mixture ratios were selected according to the replacement principle: barley 100 % (180 kg ha?¹, B100), barley 75 % + hairy vetch 25 %(135 kg ha?¹ + 22.5 kg ha?¹, B75H25), barley 50 % + hairy vetch 50 %(90 + 45kg ha?¹, B50H50), barley 25 % + hairy vetch 75 %(45 kg ha?¹ + 67.5kg ha?¹, B25H75) and hairy vetch 100%(90 kg ha?¹, H100). No chemical fertilizer was used in green manure and rice cultivation but only standard fertilizer (N-P2O5-K2O : 90-45-58 kg ha?¹) was fertilized in control plots (NPK) without green manure cultivation. The experimental design was completely randomized block with three replicates in 2013. Aboveground biomass and N accumulation of mixture was higher compared with that of pure barley and hairy vetch. Among the mixture, the highest aboveground biomass and N accumulation was observed in B25H75. The N accumulation of the mixture ranged from 169 kg ha?¹ to 186 kg ha?¹ which was much higher than amount of standard N fertilization rate (90 kg ha?¹) for rice cultivation in Korea. The C/N ratio of barley was greatly affected by mixture with hairy vetch (C/N ranging form 26 to 35) compared with pure barley (C/N 44). All mixture produced 7-8% more rice yield than the conventional cultivation (NPK) but B100 was 4-5% less than that of NPK. These results indicate that adopting mixtures between barley and hairy vetch can be efficient strategy for rice production without nitrogen fertilizer.