Provided is a method of preparing a superabsorbent polymer which exhibits more improved liquid permeability and absorption rate while maintaining excellent absorption performance. The method of preparing the superabsorbent polymer may include the steps of: performing crosslinking polymerization of water-soluble ethylene-based unsaturated monomers having acidic groups which are at least partially neutralized in the presence of an internal crosslinking agent to form a water-containing gel polymer including a crosslinked polymer; drying, pulverizing, and size-sorting the water-containing gel polymer to form a base polymer powder; performing surface-crosslinking of the base polymer powder using a surface-crosslinking solution including one or more surface-crosslinking agents in the presence of first alumina particles; and adding second alumina particles to the surface-crosslinked base polymer powder and then mixing them with each other.