The aim of this research is to explore the microecological mechanism of healthy growth and higher yield of Amorphophallus konjac under acacia forest.The content of soil nutrition was measured by normal method.Dilution method was used to measure the number of bacteria(B),fungi(F) and actinomycetes(A) in the bulk,rhizosphere and rhizoplane soils of A.konjac under acacia forest and in the farmland.Dominant microorganisms were identified by molecular techniques.The results indicated that:(1)The number of bacteria in the bulk and rhizoplane soils of A.konjac under acacia forest markedly increased by 11.8% and 588.9%,while the quantity of fungi in the rhizosphere soil significantly decreased by 74.4% compared with A.konjac in the farmland(P<0.05).(2)The quantity and percent of beneficial microorganisms in the bulk,rhizosphere and rhizoplane soils of A.konjac under acacia forest were much higher than that of plants in the farmland,while the quantity and percent of harmful microorganisms were far lower than that of A.konjac in the farmland.In the bulk,rhizosphere and rhizoplane soils of A.konjac under acacia forest,three strains were dominant species,which included Rhizobium radiobacter,Bacillus thuringiensis and Pseudomonas mosselii.In the rhizoplane soil,the quantity of Rhizobium radiobacter and Bacillus thuringiensis were 25.7 and 13.0 times as many as the number of plants in the farmland.In addition,two fungi(Epicoccum nigrum and Penicillium verruculosum) and one actinomycete Streptomyces viridodiastaticus also were dominant microorganisms.And the quantity of dominant fungi Epicoccum nigrum in the rhizoplane and bulk soils of A.konjac under acacia forest were increased by 159.2% and 120.3% compared with the control group,respectively;while dominant species Penicillium verruculosum and Streptomyces viridodiastaticus were not detected in the corresponding soils of A.konjac in the farmland.Among which,Penicillium verruculosum was occurring widely in the bulk soil,and S.viridodiastaticus was abound in the bulk,rhizosphere and rhizoplane soils of A.konjac under acacia forest.(3)Significant difference was observed in the nutrition content of soils under acacia forest and the control group.The content of organic matter in the bulk and rhizosphere soils of A.konjac under acacia forest markedly increased by 167.6% and 39.6%,while available P and K significantly decreased by 85.6% to 91.3% and 12.4% to 13.0%.It was suggested that healthy growth and higher yield of A.konjac under acacia forest was closely related to more certain beneficial dominant microorganisms and less harmful microbes in the bulk,rhizosphere and rhizoplane soils of A.konjac under acacia forest,as well as higher organic matter content.