Abstract: Ten 4-methyl-5-substitutedphenoxy-6-methoxy-8-(1-ethyl-4-amino)butylamino quinolines (10a～j) have been synthesized and evaluated preliminarily for both suppressive and causal prophylactic antimalarial activities. The results of preliminary screening test showed that three of these compounds exhibited significant activity against Plasmodium yoelii in mice, among which 10c was 4～8 times as effective as primaquine. Moreover, 10c was superior to primaquine in suppressive test against Plasmodium berghei K₁₇₃ strain in mice. On the basis of ED₅₀ and ED₉₀, 10c was about 2 times as active as primaquine. Most of other compounds showed similar activity and the minority of them exhibited lower activity compared with primaquine.