A series of the herbicidal N-(4,6-disubstituted pyrimidin-2-yl)aminocarbonyl-2-(1,1-ethylenedioxy-2-fluoro)ethyIbenzenesulfonamides, 1 and N-(4,6-disubstituted triazin-2-yl)aminocarbonyl-2-(1,1-ethylenodioxy-2-flu ore)ethylbenzenosuIfonamides, 2 were synthesized and their herbicidal activities in-vivo against rice(Oryza sativa L.), barnyard grass (Echinochloa crus-galli), bulrush(Scripus juncoides) and pickerel weed(Monochoria vaginalis presl.) were measured by the pot test under the paddy conditions. The structure activity relationships(SAR) between the herbicidal activity$(pI_{50})$ and a various physicochemical parameters of the hetero group and 4,6-disubstituents on the heterocyclic group were analyzed by the multiple regression technique. The SAR suggest that the 4,6-dimethoxypyrimidine substituent, 1a showed selective$({Delta}obs.pI_{50}=1.12)$ and the most highest activity against barnyard grass, which depend on the hydrophobicity(log P<0) of heterocyclo group and molecular refractivity$((M_R)_{opt.}=14.58cm^3/mol)$ constant of 4,6-disubstituents on the heterocyclic group.