Allelopathy of phthalic acid and propanedioic acid of root exudations of soybean on pathogenic fungi producing by root rot was studied by indoors culture experiments and statistical method.The results showed that allelopathy inhibition of high density phthalic acid and propanedioic acid（L ₅ and B ₅）on the growth of Fusarium semitectum,Cliocladium roseum and Fusarium oxysporum,especially Fusarium semitectum reached significant level or especially significant level in contrast with check.However,allelopathy promotion of low density phthalic acid and propanedioic acid on the growth of Fusarium semitectum,Gliocladium roseum and Fusarium oxysporum partly reached difference significant level.