Abstract: Comparative studies on the arthropod community between simple and complex ecosystems of longan orchards were conducted at Fengtin Town of Xianyou County, Fujian Province.The results indicated that the arthropod community in complex orchard included 13 orders,74 families and 116 species,and in the simple orchard included 12 orders, 61 families and 85 species.In the simple orchard, the ratio of quantity of phytophagous insects,predatory and parasitic insects, spiders and metatrophic insects to the whole community were 98.16%, 0.52%, 0.16%, 1.16% .respectively.Whereas in the complex orchard,they were 91.89%,3.07%,0.66% and 4.38% respectively.The richness, diversity, evenness indices and stability were higher in the complex orchard than that in the simple orchard.Compared with the simple orchard, there were more abundant species, amount and percentage of natural enemies, spiders, metatrophic insects and less pests in complex orchard.It implied that interplanting Chamaecrista nictitans in the longan orchard could effectively increase the richness, diversity, evenness and stability.It was good for maintaining natural enemies and metatrophic insects in an inhabit in order to produce in the complex orchard.So interplanting the forage in the orchard could optimize the structure of arthropod community and keep ecosystem balance.It indicated a practical way of conservation and utilization of biodiversity in longan orchard ecosystem, and it provided an effective pattern of the integrated pest management (IPM).