Introduction of a guest component into the active layer is a simple yet effective approach to enhance the performance of organic solar cells (OSCs). Despite various guest components successfully employed in the OSCs, efficient guest components require deliberate design and ingenious inspiration, which still remains a big challenge for developing high performance OSCs. In this work, we propose a concept of "structural gene" engineering to create a new "double-gene" small molecule (L-DBDD) by simply combining the structures of both donor PM6 and acceptor L8-BO. L-DBDD inherit the features of both donor and acceptor, which naturally acts as a bridge between donor/acceptor (D/A) interfaces to strengthen D/A interactions and compatibility. Incorporation of this "double-gene" small molecule into the active layer can facilitate rapid charge dissociation and simultaneously optimize molecular packing for efficient charge transport. Consequently, the ternary OSC based on PM6 : L-DBDD : L8-BO blend achieves a top power conversion efficiency (PCE) of 19.51 %, significantly suppressing the binary control device (PCE=18.52 %). These results demonstrate that the design concept of "double-gene" small molecule by combination of the "structural gene" of donor and acceptor provides a simple and meaningful guideline for guest component-assisted highly efficient OSCs.