The utility model relates to a stair, specifically speaking relates to a fabricated stair and installation method, the utility model aims at providing a dismantled and assembled fabricated stair, with prefabricated component transportation to job site, but post assembling integral hoisting, also can carry out single component hoisting, assemble waiting the floor of adorning stair, this technical scheme's fabricated stair is including prefabricated ladder beam, prefabricated straining beam, prefabricated footboard, prefabricated ladder beam sets up parallel two at least, prefabricated straining beam setting is at the both ends of prefabricated ladder beam roof beam, play the fixed prefabricated ladder beam beam action in location, prefabricated footboard setting is on prefabricated ladder beam, this technical scheme's reassembling type stair, the finished product can all be made at producing area to all subassemblies, then assemble in the place of transporting the needs installation, it is very convenient that the installation is got up, the installation method also can be set for according to the needs of actual conditions to the installation method, it installs or directly assembles on the corridor to assemble into earlier stair, can all set for by customer oneself. It is very convenient to use to reduced the cost of stair effectively, shortened the time limit for a project, can be widely used at the building field.