Avicelase is considered as an important component in the cellulases system, which has great importance in the saccharification of cellulosic materials for use in biotechnological industries. Recently, there is a trend to produce cellulolytic enzymes from microorganisms especially fungi through solid-state fermentation. In this study, a high avicelase producing local fungus was isolated and identified as Aspergillus flavus isolate L-2007/2012, then used for high avicelase production. Among some cellulosic wastes, clover husk was chosen as the best basal fermentation substrate. Results of avicelase production showed that the highest production of avicelase 799.23 U/g was obtained after 7 days of incubation by adjusting moisture ratio at 1.5:1.0 (v/w) and supplementing fermentation medium with 1% glucose as an additional carbon source and 1% ammonium sulfate as a nitrogen source. Furthermore, the highest production of avicelase occurs with incubating at 30⁰C with adjusting initial pH at 6.0 and 2 ml of inoculum (10⁶ spores/ml). By studying some factors affecting the enzyme activity, it revealed that the produced avicelase gave the highest activity at 50⁰C and pH 6.0, furthermore the enzyme has good pH stability in acidic conditions and high thermal stability at 50⁰C.