Abstract: The interfamilial hybrids between Populus alba L.×Ulmus pumila L.were described by morphological characters.In order to identify the hybrids and analyse genetic relationship between the hybrids and their parents further at the molecular level,the technique of AFLP marker was used in this study.Twenty pairs of primers were employed and 2 040 clear bands were detected.Among them,1 470 bands were polymorphic and the ratio of polymorphic bands was 72.06%.The results were as the followings:1) both gene markers of P.alba and U.pumila were exhibited on the banks of hybrids.And some new extra bands were detected in the hybrids;2) the gene marker bands of the hybrids from P.alba were more than those from U.pumila,this showed that the hybrids were maternal progenies.And the analysis of UPGMA showed similar results;3) P. alba from Liaoning station was inferred as female parent of the hybrids.Since genetic distance was the least between the clone(LP-2) and the hybrids and the variance analysis indicated that there was no significant deviation among all the samples of U.pumila,the male parent would be the clone(LP-2),also from Liaoning station;4) although the genes of U.pumila were prevalent in the hybrids,the genetic relationship between comparison clone(BP) and the hybrids was more distant.Meanwhile,the recombination ways and genetic composition of the hybrids were also discussed in this paper.