Mixed-species plantations can promote soil nutrient cycling， productivity， and ecosystem functions. Mycorrhizal associations play important roles in affecting species coexistence and nutrient cycling in mixed plantations. However， our understanding on the effects of mixed tree species with different mycorrhizal types on soil microbial community associated with soil nutrients of Eucalyptus plantations remains limited. In this study， we conducted metagenomic sequencing to investigate the changes in soil microbial community structure and functions， co-occurrence networks between bacteria and fungi， and their relationships with soil nutrients for one monospecific Eucalyptus plantation and three mixed Eucalyptus plantations with different mycorrhizal tree species， including Dalbergia odorifera（arbuscular mycorrhizal and N2-fixing， AM-NF）， Michelia macclurei（arbuscular mycorrhizal， AM）， and Quercus acutissima（ectomycorrhizal， ECM）. The results indicated that the mixed stands significantly increased the richness of soil microbial community， enhanced the abundance of genes related to soil nutrient cycling， and increased the complexity of microbial co-occurrence networks. The mixed plantations of Eucalyptus with D. odorifera had the highest soil microbial richness， relative abundance of bacterial community associated with aerobic chemoheterotrophy and fermentation， and the modularity of fungal-bacterial co-occurrence network； meanwhile， either the bacterial or fungal communities were significantly different from the other three plantations. The mixed Eucalyptus plantations with M. macclurei or Q. acutissima species had the highest abundance of microbial functional genes such as hydrocarbon degradation， nitrogen fixation， and methanotrophy. In addition， the microbial co-occurrence networks in the mixed Eucalyptus plantations with Q. acutissima have the highest number of edges， average degree， and network stability. The richness of key microbes in co-occurrence networks was closely correlated with soil