Prefabricated　steel　structures　have　certain　obvious　advantages,　that　is,　rapid　construction,　industrial　production,　and　environmental　protection.　Although　prefabricated　structures　have　been　applied　in　a　number　of　countries　in　the　world,　in　most　cases,　these　structures　are　suitable　only　for　low-rise　buildings,　and　their　applications　in　high-rise　buildings　are　nota\bly　rare.　This　paper　proposes　a　new　type　of　prefabricated　steel　structure　called　the　modular-prefabricated　high-rise　steel　frame　structure　with　diagonal　braces.　Based　on　the　T30　building,　which　is　a　hotel　building　with　30　storeys　above　the　ground,　the　mechanical　properties,　failure　mode,　failure　mechanism,　and　elastic-plastic　development　laws　of　the　structure　were　studied　via　elastic　and　elastic-plastic　design　and　analyses　under　various　load　cases　and　combinations.　The　analysis　of　the　internal　force　and　displacement　response　with　frequent　earthquakes　was　performed　using　the　response　spectrum　and　elastic　time-history　methods,　and　an　analysis　under　rare　earthquakes　is　performed　via　static　elastic-plastic　pushover　analysis.　This　paper　summarizes　the　elastic　and　elastic-plastic　structural　design　methods　and　process.　This　study　provides　important　references　for　the　design　of　this　kind　of　modular-prefabricated　high-rise　steel　structure,　and　the　design　method　has　been　compiled　into　a　design　specification　named　Technical　Specifications　for　Prefabricated　Steel　Frame　Structure　with　Diagonal　Bracing　Joints.