Phenanthridinone is a significant moiety in pharmaceutical and material science; thus, it is highly desirable to develop an efficient and robust method to construct phenanthridinone from readily available starting materials. Herein, we report a Ru-catalyzed C-H arylation of aromatic carboxylic acids with ortho-haloanilines, followed by intramolecular dehydration to afford phenanthridinones in high yields.