The project was conducted to study antagonistic activities of six strains of Streptomyces species, named as NSP (1-6) against the fungal pathogen of chili wilt disease, Fusarium oxysporum f.sp. capsici isolate FoC4. According to the dual culture method, the Streptomyces species all inhibited strongly the pathogen colony growth ranging from 75.7 to 81.0%. After that, the bioactive component of Streptomyces was produced using an enzyme production medium (EPM) by incubation with shaking for 5 days compared to 7 days, and division into 2 parts: non-filtered culture medium (NF) and filtered culture medium (F). The efficiencies of 5day-old culture media to inhibit the conidial germination were significantly higher than 7-dayold culture media, which showed inhibition of 53.6 – 62.7% for NF and 45.8 – 56.2% for F. The efficiencies of NF were higher than those of F with all of the isolates. Moreover, Isolate NSP4 showed the highest inhibition of the conidial germination. In addition, application of NSP4 reduced markedly Fusarium wilt disease in greenhouse conditions. Application of isolate NSP4 before inoculated pathogen, as prevention method, was significantly reduced disease severity (DS 2.8) higher than applied after inoculated pathogen, as eradication method (DS 3.3), while negative control (pathogen inoculation) was found in maximum scale (DS 5.0).