The present disclosure relates to a preparation method of a porous super absorbent polymer including the steps of preparing a monomer neutralized solution by adding an internal cross-linking agent, an initiator, an inorganic filler, and a nonionic surfactant to a neutralized solution obtained by neutralizing at least 80 mol % of a water soluble ethylene-based unsaturated monomer containing acidic groups; high-shear mixing the monomer neutralized solution; preparing a hydrogel polymer from the high-shear mixed monomer neutralized solution by thermal polymerization or photopolymerization; and preparing a base resin powder by drying, pulverizing, and classifying the hydrogel polymer.