Abstract: In greenhouse cucurbits of Kerman Province, Fusarium oxysporum f.sp. melonis Schlecht, Emend (Snyder and Hansen) causes root rot and fusarium wilt. To investigate for new biofungicides, antagonistic activity of soil Actinomycetes isolates were assayed against the pathogen from which Streptomyces olivaceus strain 115 showed anti-fusarium activity both in vitro and in vivo experiments. The active strain was grown in aqueous media on rotary shakers to monitor activity versus time and prepare active dry crude for further biological and physical studies. Antifungal activity was of fungistatic type on the pathogen mycelia. From the results of our studies it is clear that usage of S. olivaceus strain 115 as a biofungistatic natural product applied as an amendment in greenhouse soil mix will lead to inhibition or reduction of the pathogen effects.