A process is provided for preparing dronedarone or pharmaceutically acceptable salts thereof. The process comprises reacting 5-amino-2-butyl-3-(4-[3-(dibutylamino)propoxy]benzoyl)benzofuran (compound A) with methanesulfonyl chloride without any catalyst to provide crude dronedarone hydrochloride, which is purified to afford highly pure product. Then, the dronedarone hydrochloride can be converted to highly pure dronedarone through treatment with an alkaline solvent, the dronedarone can be further converted to other pharmaceutically acceptable salts of dronedarone. In this process, acylation between compound A and methanesulfonyl chloride is carried out successfully and the formation of the dimethylsulfonyl by-product is inhibited.