The spatial distribution and monthly fluctuation of beetle species were studied in the experimental forests of Liu-Kuei Station, Taiwan Forestry Research Institute, Taiwan. Beetles were surveyed using pitfall traps from January to December, 2004. Our result showed that species richness, abundance and Shannon diversity of beetles were significant higher in Natural Forest than those of the others, and species richness and abundance were lowest in Taiwania Plantation. The composition and trophic structure of beetle community in the Thinning Plantation resulting from thinning were compared with that in the Taiwania Plantation and natural forest. Beetles communities of Natural Forest, Taiwania Plantation and Thinning Plantation were separated from each other by ordination (PCA), meaning three forest stands have distinct species assemblages. The three group assemblages were also revealed by cluster analysis. The ground-surface air humidity, litter litter depth and herbs cover were major environment factors influencing the beetle distribution. The relative size of trophic guilds in the Thinning Plantation has changed compared to Taiwania Plantation. Detritivores increased significantly in the Thinning Plantation, suggested an increase of nutrient-cycle in the Plantation. Eight dominant beetle families that were Carabidae, Scarabaeidae, Curculionidae, Staphylinidae, Scydmaenidae, Erotylidae, Nitidulidae and Biphyllidae showed different pattern of population fluctuation. The peak mainly from March to June, and Curculionidae, Scarabaeidae, Nitidulidae also show a moderate peak in August and September. In the two plantation areas, most dominant taxa showed a similarly fluctuation patterns, which are slightly different to those of Natural Forest.