In this study, solid superacid was employed to catalyze the decomposition of steam exploded rice straw (SERS) for the production of levulinic acid, a versatile platform chemical. The results revealed that solid superacid, S2O82-/ZrO2-SiO2-Sm2O3, could be used as a substitute for homogenous acid to catalyze the production of LA from SERS and LA yield increased with the addition of solid superacid. It was also found that steam explosion combined with superfine grinding of rice straw could effectively increase LA yield for reducing particle size of rice straw and enhancing the accessibility of cellulose. Under optimal conditions of 200 degrees C, 10 min, 13.3% of solid superacid to pretreated rice straw, and 1:15 of solid-liquid ratio. LA yield of the superfine grinding SERS was 70% of the theoretical yield, which was equivalent with the homogeneous acid-catalyzed production of LA. (C) 2010 Elsevier Ltd. All rights reserved.