In　rock　engineering,　the　weakening　effects　of　water　on　the　stressed　rock　are　nonnegligible.　This　paper　studied　the　microstructure　deterioration　processes　of　sandstones　under　stress　and　stress-water　coupling　by　real-time　computed　tomography　(CT)　technology　and　compared　the　difference　in　these　two　processes.　Firstly,　the　real-time　CT　tests　were　performed　on　the　dry　and　saturated　sandstones　during　the　uniaxial　compression　to　study　the　progressive　deterioration　of　sandstones　caused　by　stress　and　stress-water　coupling,　which　were　further　quantitatively　described　by　porosity.　Then,　the　equivalent　radius　was　introduced　to　analyze　the　real-time　pore　structure　characteristics　of　sandstones　under　stress　and　stress-water　coupling.　Finally,　the　difference　in　failure　patterns　of　sandstones　under　stress　and　stress-water　coupling　was　compared.　The　results　show　that　the　real-time　CT　images　intuitively　present　the　continuous　changes　of　spatial　morphology　of　defects　in　sandstones　under　stress　and　stress-water　coupling.　During　the　uniaxial　compression,　the　porosities　of　dry　and　saturated　sandstones　decrease　at　first,　then　increase　slowly　and　finally　increase　rapidly.　However,　as　the　increase　of　stress,　the　variation　in　porosity,　shifting　of　pore　size　distribution　curve　and　change　of　maximum　equivalent　radius　interval　of　saturated　sandstone　are　more　significant,　indicating　that　even　under　the　same　stress　state,　the　water　aggravates　the　microstructure　deterioration　of　sandstone,　thus　leading　to　the　reduction　of　bearing　capacity　of　sandstone.　In　addition,　the　failed　region　of　saturated　sandstone　is　mainly　composed　of　multiple　shear　and　tensile　cracks,　which　presents　the　typical　tensile-shear　composite　failure.