With　the　development　of　Web　technology,　SaaS-as-a-Service　(SaaS)　mode　which　is　used　as　the　top-level　architecture　of　cloud　computing　has　become　a　new　concept　of　software　as　a　service　model.　How　to　design　efficient　and　secure　system　architecture　is　the　key　of　the　application　of　the　SaaS　model.　This　paper　starts　with　the　medical　information　field　service,　giving　the　solution　of　the　medical　information　service　platform.　This　scheme　is　mainly　designed　that　(multi-tenant)　and　system　security　issues　can　be　well　designed　in　SaaS　software.　©　2013　Springer-Verlag.