A study was performed to investigate the effect of reseeding rates of Italian ryegrass (IRG)〔Lolium multiflorum L.〕on its nutritive value and productivity in native grasssland of Jeju region from Oct. 2011 to Jul. 2012. IRG was sown at reseeding rates (0 30, 40 and 50 kg/ha) in native grassland. When IRG was sown, there was no draught and lodging damage. Plant height in treatment 30 kg/ha of reseeding IRG was the tallest at all harvest stages (p<0.05). DM yield in treatment of 30 kg/ha of reseeding IRG was 12,790 kg/ha and increased 2.7 folds as compared to control. However, there was no significant difference among the treatments. The content of neutral detergent fiber (NDF) significantly decreased in treatment of reseeding, compared to control (p<0.05). In general, the content of NDF in second harvest stage was lower than that of control in first harvest stage. The content of acid detergent fiber (ADF) also showed simliar trend as content of NDF. The content of total digestible nutrients (TDN) in treatments of 30 kg/ha and 50 kg/ha of reseeding were approximately 45.2% each. The content of TDN in treatments of 30 kg/ha and 50kg/ha of reseeding increased as compared to 40 kg/ha and control of reseeding (p<0.05). Therefore, it is conclued that reseeding rate of IRG may improve the yield and nutritive values of IRG at 30 kg/ha.