In order to investigate the vegetational history, paleoclimalic changes and the activity of early man in Central Taiwan, the Toushe Basin was selected as a site for palynological study. From the sediments extending down to 82 m and through 31 m of thick pcai, 40 samples were taken for this study. The palynomorphs were extracted by chemical dcflocculation, then permanent slides were prepared by scaling with paraffin. Based on the examination of the permanent slides, a hypothesis for the vegetational history and past climate is proposed as follows: A warm temperate period has prevailed in this area ever since the formation of the lake. Except for scanty pollen zones such as Zone A (8200-7100 cm), Subzone Cl (5900-5300 cm), Subzonc C3 (5150-4800 cm) and Subzone C5 (4200-3900 cm), successive series of plant communities have been found as follows: starting at a depth of 71 m, we find that Subzone B1 (7100-6750 cm), has a Quercus-Symplocos-Pasania-Alnus association, Gramincac-Compositae-Typha subassociation; Subzone B2 (6750-5900cm), Quercus-PasQnia-Alnus-Salix-Carpinus association, Gramineae~Cyperaccae subassociation; Subzone C2 (5300-5150cm), Pasania-Quercus-Myrica-Symplocos iation, Gramincac-Cypcraceae subassociation; Subzone C4 (4800-4200 Pasarua-Quercus-Xfyrica-Symplocos-Ligustrum-Engelhardiia association, Gramineae-Cyperaceae subassociation; Subzonc C6 (3900-3100cm), Pasania-Quercus-Myrica-Symplocos-llex-Salix-Engelhardtia association, Gramineae-Cyperaceae subassociation; Subzone D1 (3100-1600cm), Alnus-Symplocos association, Gramineae-Cyperaceae subassociation; Subzone D2 (1600-1350 cm), Alnus-Symplocos-Ligustrum-llex association, Gramincac-Compositac subassociation; Subzone D3 (1350-975 cm), Pasania-Quercus-Alnus-Symplocos-Ilex-Salix-Ulmaceae-Mallotus association, Gramineae-Cyperaceae subassocia-tion; and Zone E (975 cm-surface), Uquidambar-Malloius-Pinus-Ulmus/Zelkova association, Gramineae-Cyperaceae subassociation. From the evidences of charcoal at 670 cm (ca. 3850 years B. P.), and wood fragments with burning iraccs at S80cm (ca. 3400 years B. P.) and a sleep rise in deposition rate of sediments since 4500 years ago, we suggest that early man may have come into this district to clear the forest as early as 4500 years ago.