A　soil　water　characteristic　curve　(SWCC)　can　describe　the　relationship　between　unsaturated　soil　matric　suction　and　water　content.　By　analyzing　and　researching　the　test　data　of　the　soil　water　characteristic　curve　researchers　can　initially　establish　the　SWCC　equation　and　apply　this　equation　to　the　actual　engineering　analysis.　In　another　words,　this　article　is　based　on　the　fluid-solid　coupling　theory　of　unsaturated　soil　used　to　analyze　and　study　the　problem　of　land　subsidence　caused　by　tunnel　construction.　Numerical　calculations　show　that　the　coupling　results　agree　well　with　the　measured　curve　works.