Information is needed on the plant characteristics affects by forage removal and their relationships to grain yield of italian ryegrass in order to combine herbage seed crop management and livestock farming. This study with tetraploid cv. Tetrone was carried out on the experimental field of Haenam Branch Station. treatments included two different seeding time, cutting time and frequency. Seeds were sown in row 50 cm width within the rows. The results are summarized as follows: 1. Fresh and dry matter were increased significantly in plots defoliated lately and many times but seed yield components were decreased significantly in plots defoliated in spring. 2. Autumn defoliation had no significant effect on the seed yield but seed yield were decreased significantly in plots defoliated later than 8 April. 3. Excess vegetative growth can be removed in autumn and early spring without harm to the seed crop and the most important aspect of its removal is the timing of the operation. 4. Seed yield reductions were accompanied by the decrease of inflorescences,seeds/spike, and thousand seeds weight, due to an increase in apex removal of vigorous tillers by late cutting.