An antagonistic bacterial strain BTF5 against Fusarium oxysporum f.sp.niveum was isolated from rhizosphere soil collected from continual watermelon mono-cropping by dual-culture,and identified according to morphology,biochemical assay and homology analysis of 16S rDNA sequence.The results showed that inhibition rate of the strain BTF5 against F.oxysporum f.sp.niveum was up to 63.09% in the antagonistic experiment.Compared with sequences listed in the Gen Bank database,strain BTF5 had the highest genetic similarity with Burkholderia vietnamiensis and homology is 99%.Less change in the inhibition effect of antagonizing against growth of F.oxysporum f.sp.niveum was observed during eight generations of transfers on artificial media,indicating its potential biocontrol efficacy and application prospect.