Abstract: Capsicum-maize relay intercropping pattern, as an ecologically efficient and high-yield system, is a promising management practice widely used in northwest China. An experiment with different capsicum-maize intercropping systems was conducted to determine the effects of relay intercropping maize on microbial ecological characteristics of rhizosphere soil in capsicum field. The intercropping systems included no partitioned intercropped capsicum and maize (ICN), and nylon-mesh partitioned intercropped capsicum and maize (ICM), plastic-film partitioned intercropped capsicum and maize (ICP), and sole capsicum (SC). The traditional dilution plate method, chloroform fumigation method, BIOLOG GN system and inter-specific root separation techniques were adopted to determine the microbial amount, microbial biomass nitrogen and carbon, and diversity of microbial community. The results showed that the trend of total microbial amount in rhizosphere soil was same at that of bacterial amount at any growth stages of capsicum. The amounts of fungi, bacteria and actinomycetes and the ratios of fungi to actinomycete and bacteria to actinomycete counts of ICN treatment and ICM treatment were slightly higher than those of SC treatment and ICP treatment. Compared with other treatments at full fruiting stage, ICN increased soil microbial biomass C and N respectively by 14.2%~54.0% and 10.6%~54.7%. BIOLOG analysis showed that the curve between Average Well Color Development (AWCD) and incubation time was S-shaped for all the treatments. Relay intercropping of capsicum and maize not only significantly (P < 0.05) increased Shannon-Wiener index, meeting rate of different plant species (PIE), Simpson index and Mclntosh index of soil microbial community, but also enhanced soil microbe sole-carbon-source utilization. Correlation analysis revealed that the correlation between different diversity indexes of rhizosphere soil microbe community and biological yields of capsicum were either partially (P < 0.05) or fully (P < 0.05) significant. The findings suggested that root interaction between intercropped crops enhanced the population of microorganisms and carbon-metabolic microbial diversity in rhizosphere soils under capsicum-maize relay intercropping system.