Although elevated CO2 (eCO(2)) significantly affects the -diversity, composition, function, interaction and dynamics of soil microbial communities at the local scale, little is known about eCO(2) impacts on the geographic distribution of micro-organisms regionally or globally. Here, we examined the -diversity of 110 soil microbial communities across six free air CO2 enrichment (FACE) experimental sites using a high-throughput functional gene array. The -diversity of soil microbial communities was significantly (P<0.05) correlated with geographic distance under both CO2 conditions, but declined significantly (P<0.05) faster at eCO(2) with a slope of -0.0250 than at ambient CO2 (aCO(2)) with a slope of -0.0231 although it varied within each individual site, indicating that the spatial turnover rate of soil microbial communities was accelerated under eCO(2) at a larger geographic scale (e.g. regionally). Both distance and soil properties significantly (P<0.05) contributed to the observed microbial -diversity. This study provides new hypotheses for further understanding their assembly mechanisms that may be especially important as global CO2 continues to increase.