Abstract: Lactobacillus paracasei L1 which isolated from the sweet potato acid steeping liquor could combine with the starch to produce amylase and resolve the starch.This experiment was to study the effect of different culture condition on the production of amylase and the effect of temperature and pH to the activity of amylase. Through single factor and orthogonal experiments, the condition of enzyme production was optimized. The results showed that the Lactobacillus paracasei L1 could produce the highest amount of amylase when the initial culture medium pH was 4.0, culture temperature was 42℃, 6% of potato starch was taken as carbon resource and when it was cultured 96h. The amylase produced by Lactobacillus paracasi L1 has relevant high activity under acidic conditions.The amylase activity was highest when the pH was 4.0, and the optimum reaction temperature for the amylase was 40℃.Under this conditions, the highest activity of amylase could reach 102.95U /mL. Lactobacillus paracasei L1 which used starch without gelatinizing could produce more amylase than which of using starch with gelatinizing.That means Lactobacillus paracasei L1 could use raw starch to produce amylase.