The present invention provides a green catalytic process for the synthesis of acetyl salicylic acid using solid acid catalysts at atmospheric pressure. The invention involve the solid acid catalyst such as sulfated transition metal oxides namely nano-crystalline sulfated zirconia, sulfated titania; modified zeolites namely zeolite H-beta, H-Y, H-ZSM-5 and K-10 montmorillonite clay in a solvent free environment using salicylic acid and acetic anhydride with yield about 95% and high selectivity (100%). The solid acid catalysts can be recovered, regenerated and reused.