The invention discloses a cyclic diol modified water-borne polyisocyanate curing agent as well as a preparation method and an application thereof. The preparation method comprises steps as follows: 75%-90% by mass of polyisocyanate, 0.01%-0.5% by mass of an antioxidant, 1%-10% by mass of cyclic diol and 5%-21% by mass of hydrophilic polyether are sequentially added to a reaction kettle under the protection of nitrogen, the temperature is increased to 40-80 DEG C, the reaction is performed for 6-8 h, when the content of NCO in the system reaches a theoretical value, 0.01%-0.5% by mass of a terminating agent is added to terminate the reaction, and a product is obtained. The water-borne polyisocyanate curing agent prepared with the method has the advantages that the synthesis process is simple, product storage is stable, and a prepared double-component water-borne polyurethane coating is high in film drying speed, high in hardness and good in medium resistance and has longer construction working life.