1. Two strains of Aspergilli producing acid resistant amylase were isolated from air. The strain U^(-1) and U^(-2) were similar to Asp. usamii tan type mutant in the morphological characteristics. 2. The influence of cultural pH for production of amylase were investigated in the suface culture, it was different each other in the cultural optimum initial pH. The activity of acid resistant amylase produced by strain U^(-1) was higher than that of strain U^(-2). The acid resistance was increased by culturing in lower pH. 3. The lower initial pH (U^(-1) pH 4.0, U^(-2) pH 2.0) was better than neutral (pH 6.0) for the production of amylase and growth of them. The effect of low initial pH for the production of amylase was not to accelerate but caused by change of pH in the cultural process, in the range of this experiment.