Abstract: Objective To study the effects of di-n-butyl phthalate(DBP)on the fecundity and the life span in drosophila melanog aster.Methods Drosophila melanogasters were divided randomly into four gr oups and were continuously fed with medium containing 0%,0.2%,0.6%,1.8% DBP during entiretrial period.The eclosion numbers of filial generation flies and the surviving numbers of parent flies were observed and recorded daily.Results The percent of sterility of drosophilas in DBP groups were higher than that in control group;the average reproduction of flies in 1.8% DBP group was observably reduced as compared with control group(P<0.05).The average proreation days and the average life span of flies in DBP groups were gradually shortened with the rise of DBP concentration.Conclusion DBP can interfer flies.natural development and metabolism;reduce flies.fecundity;shorten flies.life span obviously in some deg ree.