This study was conducted to investigate the vegetational succession on improved pstures in Choju-do. The results obtained were summarized as follows: 1. Number of weed species were increased in course of year after pasture inprovementsixty cne species were surveyed on the first pastures and forty six species on the sixth year pastures. 2. As year went on, abundance of introduced grasses was dereasod rapidiy 0.03 per cent on the sixth year pastures but that of weeds was increased. 3. This tendency of abundance was similar to the coverage of introduced grasses and weeds. 4. In course of year, Imperata cylindrica and Zoysia japonica showed marked increase but Centella asiatica, Digitaria sanguinalis and Artomisia asiatica were decreased in the abundance and the coverage. 5. The vegetation was Dactylis glomerata/Trifolium repens type on the first and the second year pastures, Imperata cylindrica/Trifolimn repens type on the third and the forth year pastures and Imperata cylindrica/Zoysia japonica type on the fifth and the sixth year pastures.