A sealant and a preparation method thereof, a display panel motherboard and a manufacturing method thereof are disclosed. The sealant includes a main adhesive material and a water swellable material dispersed and doped in the main adhesive material. The sealant and the preparation method thereof, the display panel motherboard and the manufacturing method thereof are capable of solving a problem of a notch formed in a sealant where a etchant flows into the display panel unit when the display panel mother board is subjected to a thinning treatment.