In this paper,the allelopathy of aqueous extracts from different organs of Sonneratia apetala on the seed germination of S.caseolaris and S.apetala were studied.The following results were obtained:1)Aqueous extracts from different organs of S.apetala inhibited the germination of S.caseolaris.At high concentration,the germination of S.caseolaris was significantly inhibited;2) Aqueous extract from S.apetala roots inhibited the radicle length of S.caseolaris.At high concentration the radicle length was inhibited significantly,while with decreasing concentration,the inhibitory effects got weaker.Applied with the extracts of S.apetala branch,leaf and fruit,the radicle length of S.caseolaris was significantly inhibited at high concentration;while with decreasing concentration the inhibitory effects got weaker and even turned into stimulating effects.3)Applied with the extracts from different organs ofS.apetala,the germination orS.apetala was stimulated at low concentration and inhibited at high concentration.4)At high concentration of aqueous extract from S.apetala fruit,the radicle length of itself was inhibited significantly,while with decreasing concentration the inhibitory effects got weaker.Applied with the aqueous extracts of S.apetala branch,leaf and fruit,the radicle length of S.caseolaris was stimulated at low concentration and inhibited at high concentration;5)As to the inhibitory effects on the germination and radicle length of S.apetala and S.caseolaris,the effects of aqueous extract from Sonneratia apetala fruit were stronger compared with that of other organs.