The invention discloses a method for preparing 16a-hydroxy prednisolone. The method includes the steps of adopting 17a-dehydroxyl prednisolone as a raw material and making the 16th locus and 17th locus of initial raw material 17a-dehydroxyl prednisolone subjected to an epoxidation reaction with organic peracid in a first organic solvent to obtain an epoxy object; making the epoxy object reacted with glacial acetic acid for ring opening under catalysis of acid catalysts in a second organic solvent to obtain 16a,21-diacetoxy prednisolone; then dissolving 16a,21-diacetoxy prednisolone in a thirdorganic solvent, hydrolyzing acetate at two positions under the catalytic action of a solid-phase base catalyst, and preparing 16a-hydroxy prednisolone, wherein the solid-phase base catalyst adopts aluminum oxide and silica gel or calcium carbonate as carriers, and the catalysts of sodium carbonate or sodium hydroxide are adsorbed on the carriers. 16a-hydroxy prednisolone is prepared by means of the efficient, environment-friendly and economical method.