Abstract: In search of herbicidal compounds,based on the structure of 4-heptyloxy(octyloxy)benzamidine and its binding pattern with ketol-acid reductoisome-rase (KARI),a series of heterocyclic compounds containing heptyloxyl or octyloxyl group on 4-position of benzene ring were designed and synthesized.The 26 synthesized compounds(22 of which are novel ) were confirmed by elemental analysis,1H NMR,IR and MS.The preliminary biological assay indicated that most of the compounds showed rice KARI inhibitory activity and herbicidal activity.Among 26 compounds, 9a and 9b showed 65.7% and 71.1% inhibitory activity on rice KARI at the concentration of 200 μg/mL; 78.6% and 89.0% on rape root (Brassica campestris) at 100 μg/mL concentration,repectively.