We isolated 640 isolates from sunflower rhizosphere. Eighteen antagonistic bacteria screening have against Sclerotinia sclerotiorum. Isolate XRK5 has obviously and steady antibiosis against the pathogenic fungus, and it implys that XRK5 has good application potentiality. Based on the results of morphological characteristics, physiological and biochemical properties and phylogenetic analysis of 16S rRNA, XRK5 was identified as Lysobacter capsici. The sequence of 16S rRNA obtained in this study has been submitted to GenBank and the accession number is FJ959348.