Large-span tensioning steel structure and construction method

The large-span tensioning steel structure comprises a first fixing steel part and a second fixing steel part, mounting structures are mounted at the bottom end of the first fixing steel part and the bottom end of the second fixing steel part in an embedded mode, and mounting structures are mounted on the top end face of the first fixing steel part and the top end face of the second fixing steel part in an embedded mode. A fixing steel rope is installed on one side of the second fixing steel part in an embedded mode, and the top end of the second fixing steel part is detachably sleeved with a fixing gear assembly. A driving motor drives a driving shaft center to rotate, then the driving shaft center drives a driving gear to rotate in an engaged mode, an auxiliary wheel and rotating teeth are sequentially driven to rotate, and therefore a fixing head on one side of a mounting top plate is driven to rotate; and therefore, the fixing steel rope at the other end of the fixing head is wound at the bottom end of the