Abstract: Disclosed herein is a one-component type moisture-curable polyurethane composition with improved storage stability. The polyurethane composition comprises a prepolymer prepared by reacting a polyol having a weight-average molecular weight of 1,000 to 5,000 with a mixture of an aromatic diisocyanate and an aliphatic diisocyanate in a weight ratio of 1:1 to 1:0.1, an inorganic paste, and a blocked amine compound and a monomeric vinyl silane as additives for removing moisture from the inorganic paste. The polyurethane composition has improved storage stability even in general open equipment. Further disclosed is a method for preparing the polyurethane composition.