The invention relates to an attaching slab supporting seat device with an adjustable pull rod and a construction method. The attaching slab supporting seat device with the adjustable pull rod adopts the structure that an attaching slab supporting seat is fixed to the edge of each layer of a main structure through bolt assemblies, a guiding seat is mounted on each attaching slab supporting seat, a hanger is fixed on each layer of the main structure through the bolt assemblies, each layer of the attaching slab supporting seat and the hanger on the upper layer are fixed through the adjustable pull rod, and the guiding seat on each layer of the attaching slab supporting seat is fixed to the next layer of the attaching slab supporting seat through an adjustable counter pull rope so as to prevent upturning. According to the attaching slab supporting seat device disclosed by the invention, a force transferring system combining upwards hanging with downwards pulling is adopted, the modeling structure of cantilever slabs of a building is masterly avoided, a force-bearing body of an outer hanging scaffold of the building is transferred to a building body, and the attaching slab supporting seat device has the advantages that the construction difficulty and the construction strength are reduced, the construction progress is accelerated, the cost is low, and the attaching slab supporting seat device can be recycled.