The present invention relates to a method for preparing a polyether-modified HMDI aqueous polyurethane curing agent, which mainly consists of a hydrogenated diphenylmethane diisocyanate H6MDI or H12MDI, a polyether polyol, an inert solvent and a polymerization inhibitor; the polyether-modified HMDI aqueous polyurethane curing agent prepared in the present invention does not contain an aromatic hydrocarbon, a glycol ether and an alkylphenol, and has characteristics such as environmental protection, a good scratch resistance, a good transparency, an excellent chemical resistance, a strong contamination resistance, a good yellowing resistance, etc. A polyurethane paint, formulated from the curing agent and an aqueous hydroxy component, has characteristics such as a high hardness, a high transparency, a good paint film scratch resistance, a good levelling performance, a high fullness, a good intermiscibility, etc. The polyether-modified HMDI aqueous polyurethane curing agent is widely used as a special curing agent in various bicomponent aqueous polyester paints, aqueous polyurethane paints, aqueous epoxy paints, aqueous alkyd paints, and aqueous polyurethane glues, etc., such as an aqueous wood paint, an aqueous industrial paint, an aqueous plastic paint, etc.