ActinomycetesBCy has been isolated from Seagrass Cymodocearotundata, Prapat Agung Coastal Bali Barat, Indonesia. Identification by 16S rRNA showed that the colony belongs to genus Streptomyces. The isolate was grown in two different broth media, Bushnell-Haas (BH) and Production Medium 4 (PM4) for 1 and two weeks. The medium was filtred and dry weight of biomass was measured. Filtrate was extracted using ethyl acetate and also measured for dry weight. Based on dry weight of biomass within two weeks, it showed that Streptomyces sp.BCy grew better in PM4 (700 mg/100 mL) compare to BH (166.8 mg/100 mL). Weight of crude extract in PM4 (15.6 mg/100 mL) also higher than the weight in BH (4.3 mg/100 mL). Antimicrobial activities of crude extract were carried out by Kirby Bauer method and determined by diameter of clear zone. The antimicrobial activity of crude extract more effective in two weeks and were able to inhibit Staphylococcus aureus NBRC 100910 and Candida albicans UICC Y-29.