Soil　microbe　plays　an　important　role　in　terrestrial　ecosystem,　and　it　is　the　core　of　the　biological　geochemical　cycle,　which　has　a　significant　impact　on　the　process　of　material　circulation　and　transformation　and　energy　flow　in　soil　ecosystem.　In　this　study,　a　short-term　indoor　culture　experiment　has　been　carried　out　with　seedlings　soybean　(Yudou　19)　as　the　test　plant.　Three　kinds　of　soil　water　gradient(80%,　60%,　40%　WHC)　and　two　kinds　of　CO2　concentrations　(350　ppm,　700　ppm)　were　set　to　study　the　changes　of　soil　microbial　biomass,　soil　microbial　community　structure　and　functional　diversity　under　the　control　of　environmental　factors,　and　to　discuss　the　response　law　of　soil　microbes　to　simulated　climate　change　(drought　and　atmospheric　CO2　doubling),　so　as　to　provide　a　new　idea　for　the　exploration　of　the　possibility　of　soil　microbial　enhancing　or　weakening　global　climate　change.　Atmospheric　CO2　doubling　can　significantly　promote　plant　photosynthesis　and　can　alleviate　and　compensate　the　inhibition　of　drought　stress　on　plant　photosynthesis　in　a　certain　range.　Drought　stress　will　result　in　a　significant　increase　in　the　content　of　soluble　organic　carbon　in　soil,　while　CO2　doubling　have　no　significant　effect　on　the　content　of　soluble　organic　carbon　in　soil.　Therefore,　it　is　possible　for　atmospheric　CO2　doubling　to　accelerate　the　transformation　of　soil　carbohydrates,　increase　the　rate　of　degradation　of　soil　organic　carbon　pool　by　increasing　microbial　biomass,　and　have　a　negative　impact　on　climate　change.　While　drought　stress　could　release　the　circulation　of　soil　carbon　pool　to　some　extent.