Research about amylase activity of 28 isolates of actinomycetes isolated from mangrove litter at Pramuka Island, Kepulauan Seribu, DKI Jakarta, Indonesia, has been carried out. Amylase activity was screened using the iodine method with starch agar containing 0.1 % soluble starch, then expressed as amylase Activity Index (AI). Among the tested isolates, SM 25 was the most potential isolate for amylase activity with AI=3.21 which was further tested. Amylase activity of isolate SM 25 was measured using the dinitrosalicylic acid (DNS) method with starch broth 2 % containing soluble starch or rice flour. The concentration of reducing sugar in the growth medium was also measured after 4 days incubation. The result showed that isolate SM 25 has higher amylase activity in medium with soluble starch (5.02 U/mL) than rice flour (3.33 U/mL). However, the concentration of reducing sugar was higher in medium with rice flour (582.42 μg/mL) than soluble starch (407.40 μg/mL).