To develop BCL6 inhibitor for treatment of ovarian cancer, we established HTRF and BCL6 luciferase reporter screening system, and finally WK369 was identified as a novel BCL6 inhibitor, which could disturb the interaction between BCL6 and SMRT at low concentrations and significantly re-activate the BCL6 target genes in vitro. Here, BCL6 is linked to ovarian cancer.