The condensation of several aromatic/heteroaromatic aldehydes with 2-aminothiophenol catalyzed by cellulose sulfuric acid in the solid-state by grinding method under solvent-free conditionafforded 2-arylbenzothiazoles. This method provides several advantages including environmental friendliness, short reaction times, high yields and a simple work-up procedure. Moreover, the catalyst was successfully reused without significant loss of activity.