Abstract: With soluble starch as carbon source and dodecyl benzene sulfonic as sulfonating agent,carbon-based solid acid with SO3H functional groups was prepared via synchronous carbonization-sulfonation method.The sulfonated samples were characterized by means of SEM,EDS,FTIR,XRD and TG.Then the catalysts were examined as solid acid catalysts in acetylsalicylic acid synthesis.The better conditions obtained via single factor tests was that the percent by weight of carbon-based solid acid to raw material was 4.5%,the molar ratio of acetic anhydride to salicylic acid was 2.0∶1,acylation reaction temperature was 75 ℃,reaction period was 25~30 min.The yield of acetylsalicylic acid was 82.8% under the action of carbon-based solid acid catalyst and 76.5% under the action of catalyst recycled for five times.