The strain of Aspergillus, 6368A, producing acid protease showing high activity was isolated from soil, as a result of wide research about mold group. This strain was identified as a species of Aspergillus tubingensis by the investigation of morphological characteristics. The change of the enzyme production under the various media and culture condition was also studied. The optimum pH and stability of crude acid protease are 2.5, 2.0~4.5 and the optimum temeprature and thermal inactivation waas shown $50^{circ}C,;55^{circ}C$, respectively. From the result of the study on the effects of metal ions, it was found that $MnCl_2,;CoCl_2,;CuCl_2,;SrCl_2,;and;NiCl_2$ slightly increased the enzyme activity, on the other hand $ZnCl_2,;CaCl_2,;MgCl_2,;SLS,;and;KMnO_4$ decreased it.