Litter decomposition is the key process in nutrient recycling in the terrestrial ecosystem. A clear knowledge about how litter diversity affects composition and abundance of the soil microbial community and then potentially changes the microbiological mechanism of litter decomposition will help understand the relationship between biological diversity and functions of a forest ecosystem. A pot experiment was carried out to compare mixed litters from massion pine, slash pine, white oak and blue Japanese oak, which are all typical species of the hilly red soil regions in South China, with litter of conifer leaves only in effect of their decomposition on soil microbial community structure with the PLFA method. Results show that (1) the mixed litter treatment was lower in total PLFA, in relative abundance of fungi and in fungi/bacteria of the soil microbial community, but higher in relative abundance of bacteria and actinomyces than the single litter treatment. And the difference in soil microbial biomass between the treatments was contributed mainly by fungi; (2) The principal component analysis (PCA) of the PLFA data demonstrated that mixed litter treatment differed significantly from the single litter treatment in soil microbial community structure. Principal component one (PC1) explained 65.74% and 89.63% of the variation respectively in the two decomposition periods (9 and 18 months). PC1 consisted mainly of fatty acids of 18:2ω6,9、18:1ω9c, 17:0 and 10Me18:0; (3) Soil microbial community structure was affected by initial carbon-nitrogen ratio (C/N) and lignin-nitrogen ratio (lignin/N) of the litter, which were negatively related to relative the abundance of bacteria, but positively to the relative abundance of fungi and fungi/bacteria in the soil microbial community. Decompositions of mixed conifer-broadleaved leaf litters provided a more favorable microenvironment for decomposers by changing the chemical composition of the litters such as carbon-nitrogen ratio and lignin-nitrogen ratio.