Abstract: In this experiment, the role of extracellular polysaccharides ( EPS) and lipopolysaccharides (LPS) werestudied by detecting the number of Ralstonia solanacearum in Eucalyptus urophy lla ×E. grandis root adsorp tion andingression. The results showed that the number of GN1 and 93B in adsorp tion and ingression increased obviouslywhen the rootswere treated with EPS, while decreased evidently with LPS in 6 h after inoculation. The number ofbacteria washed off EPS decreased evidently in adsorp tion and ingression to the roots. In comparison, the number ofbacteria washed off both EPS and LPS had the same decreasing tendency, but not so evident as the former. Theseresults demonstrated that EPS p layed a role in enhancing the adsorp tion and ingression of R. solanacea rum to theroots of Eucalyptus urophy lla ×E. grandis, while LPS had inhibitory effect.