The Hwaomsa valley forest and the Piagol valley rarest in Mt. Chiri were studied to investigate forest structure and succession. Thirty plots in the Hwaomsa valley forest and thirty-nine plots in the Piagol valley forest were set up, and vegetation analysis of TWINSPAN classification and DCA ordination was carried out. The size of each plot was 20m $ imes$ 25m, and the trees above 2cm DBH in each plot were measured. The Hwaomsa valley forest and the Piagol valley forest were classified into four communities and three communities by the altitude, respectively. The successional trends of major tree species seem to be from Pinus densiflora and Quercus mangalica through Quercus serrata to Carpinus spp. in the Hwaomsa valley forest. and from Quercus mongalica through Quercus serrata to Carpinus Spp. in the Piagol valley forest. The Hwaomsa valley is assumed to be interfered by the man more, and develop into the climax less than the Piagol rarest.