The utility model provides an unload support plate subassembly relates to the building field, and it includes the pivot and connect in the support plate that unloads of pivot, and lieing in the support plate that unloads of pivot both sides, be first respectively and unload the support plate and the second unloads the support plate, and the first area that unloads the support plate is S1, and the first uninstallation plate -type heart be L1 to the distance of pivot, and the area that the second unloaded the support plate be S2, and the second is unloaded the distance that the plate -type heart arrived the pivot and is L2, wherein, and S1L1>, S2L2. The utility model discloses an it is unbalanced to unload the relative pivot both sides atress of support plate, makes to unload the support plate and receive a deflecting force all the time, and automatic the emergence is deflected when the deflecting force that receives is enough big, reduces the lifting surface area, has reached the effect of off -load, the effectual destruction that has prevented because of the unload support plate subassembly overload leads to the fact. The utility model discloses an unload support plate subassembly is a simple structure, can sheds the unload support plate subassembly of load.