A support device for a tire sealant inflator contains: a C-shaped rib on which two spaced plates are engaged when inflating and supplying sealant into a broken tire, and the tire sealant inflator and the support device are connected so as to exert the tire sealant inflator stably. The support device further contains a base, and the base includes a C-shaped holder formed thereon, an opening defined on a side of the C-shaped holder, and the C-shaped rib extending inward from a top of the C-shaped holder.