Our previous studies found that biodiversity in soil of Eucalyptus grandis plantations gradually decreased at the initial four years after afforestation, but then significantly increased. Therefore, in this study, we studied the community structure of soil fauna at the stand age of four and at the age of eight, which is usually considered to be a regular rotation period for E. grandis. Three densities (D1:2000, D2:1600, D3:1200 ind/hm²) were selected to compare community structure of soil fauna among above age groups. Picking up, Tullgren funnel and Baermann methods were used to collect the macro, meso and micro soil fauna in Danling County, Sichuan Province. The results showed that:1) in total, 2904 individuals of soil fauna were collected, which belonged to 4 phyla, 8 classes, 22 orders, and 70 families. There were 541 macro individuals dominated by Formicidae and Campodeidae, and 2636 individuals of meso-micro fauna dominated by Galumnidae, Isotomidae and Nemata. 2) There were differences in group numbers, individual numbers, and densities of soil fauna between forest ages and stand densities. The individual numbers of soil macro fauna in 4-year old E. grandis plantation increased significantly with the decrease of density. Both group and individual numbers of meso-micro fauna in 8-year old E. grandis plantation increased significantly with the decrease of density. Both group and individual numbers of soil fauna in D1 density were higher in 4-year old stand than those in 8-year old stand. The remaining density was the opposite. 3) The soil fauna diversity indexes were significantly affected by forest density. The Margalef richness index of soil macro fauna in 4-year old E. grandis plantation increased significantly as forest density decreased. While the shannon-wiener index and Margalef richness index of soil meso-micro fauna in 8-year old E. grandis plantation increased significantly with the decrease of density. 4) The soil macro fauna in the E. grandis plantation were mainly omnivores, followed by debris-feeder's. The soil meso-micro fauna were mainly saprozoic, followed by omnivores. 5) RDA analysis indicated that the soil fanual communities were mainly affected by following environmental factors:forest density, soil moisture content, soil pH, and total nitrogen content. Soil fauna belonged to Oppiidae, Orchesellidae, Parasitidae, Staphylinidae, and Liacaridae were greatly affected by above factors at 4-year old of E. grandis plantation, while those belonged to Nemata, Blattidae, Campodeidae, Lacclapidae, and Onychiuridae were greatly affected by above factors at 8-year old of E. grandis plantation. Therefore, prolonging rotation period and reducing the forest density appropriately is necessary to improve the stability, increase biodiversity of soil fauna, and thus promote the stability of community structure of soil fauna in E. grandis plantation.