The invention relates to a method for preparing cubic NaNbO3 with square holes and belongs to the field of photocatalytic materials. The preparation method comprises that antimony pentachloride, sodium hydroxide and sodium nitrate as raw materials are treated through a hydrothermal method at 180-240 DEG C for 36-60h to produce the cubic NaNbO3 photocatalytic material with square holes. The cubic shape with square holes is conducive to light absorption and pollutant adsorption, greatly improves the adsorption capacity of the photocatalytic material and improves the rate of photocatalytic degradation. The preparation method realizes a low cost, has simple processes, is easy to operate and does not need complicated equipment.