Indonesia is rich in natural resources, including source of biofuel such as sweet potato starch. Sweet potato (Ipomoea batatas L) has a starch content of 22.4% which could be converted to sugar through hydrolysis process in order to yield ehtanol. This study aimed to examine the optimize ethanol yielded from starch of sweet potatoes using combination of acid and enzymatic hydrolysis. It used 0.5 HCl which combined with each Aspergillus flavus and Aspergillus niger, and mixture of both microbes for acid and enzymatic hydrolysis process. The highest sugar content resulted in hydrolysis process was fermented for 24, 48, and 72 hours to yield maximum ethanol. Data were analyzed using one-way analysis of variance (Anova). The highest reducing sugar produced by combination of HCl and Aspergillus niger was 12.61% (w/v). The highest ethanol produced was 46.17% (v/v) in 72 hours fermentation time.