Ancient tea garden has existed in Lancang County, Yunnan Province for more than 1,300 years, and is regarded as the provenance of Pu’er Tea’s seed source. The ancient tea garden ecosystem is a typical model that integrates conservation biodiversity and utilization of natural resources. In order to reveal the role of biodiversity conservation of this ecosystem, plant diversity and application value of ancient tea gardens, normal tea gardens and secondary forestry communities in Lancang County were surveyed and compared. 360 households investigation were also conducted by using household-based agro-biodiversity assessment (HH-ABA). The results showed: (1) Ancient tea garden communities have high biodiversity, whose plant species diversity (H = 3.03) is lower than that of secondary forestry (H = 4.59) and higher than that of normal tea garden (H = 2.62); (2) Life forms analysis of plant species showed the vertical structure of the ancient tea garden communities are intact, herbs, trees, shrubs, vines, epiphytes are included, which is similar to that of secondary forest, while normal tea garden is dominant by herbs and no trees; (3) A large number of protected species, including five endangered, seven vulnerable and three rare, is well conserved in the ancient tea garden, while no protected species were found in secondary forest and normal tea garden; (4) The analysis of agro-biodiversity revealed that 56 % of plant species in the ancient tea garden are effectively used by households, while no plant except tea trees is used in normal tea garden; (5) The integrated values of ancient tea garden and normal tea garden illustrated that both biodiversity conservation and economic income of ancient tea garden are higher than that of normal tea garden. We suggest that the local peoples’ knowledge and experience on resource management and utilization should be well documented and encouraged, and effective conservation and reasonable utilization of ancient tea garden would be achieved through training and demonstration with the participation of the local government, research institution and farmer.