The surface of diamond powder (DP) was sulfonated via a covalent modification method using 1,3-propanesultone, for the fabrication of a new class of solid acid material. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy studies confirmed Successful introduction of sulfo groups on the DP Surface. The optimal condition for the preparation of sulfonated DP (S-DP) was investigated in terms of acid amount on the Surface. The S-DP exhibited solid Bronsted acid properties in pure water and catalytic activity toward the formation of ethyl acetate.