Disclosed herein is a method or process for preparing erythromycin thiocyanate, which belongs to the pharmaceutical field. Also disclosed herein is a method of using erythromycin or a salt thereof as a raw material, which can be dissolved in acetone or a mixed solvent containing acetone to yield erythromycin thiocyanate A as the main component and low in the content of impurities. Said erythromycin thiocyanate could be used as the raw material for preparing Azithromycin and Clarithromycin, which meets the standards made by European Union and US.