In this paper, Shannong 87074-519, a derivative of wheat-decaploid Elytrigia elongata, was identified by inoculation assessment, cytological analysis, simple sequence repeat (SSR), molecular marker technique,and genomic in situ hybridization (GISH). The results are as follows: the chromosome number of Shannong87074-519 in root tip cells was 2n=44, 22 bivalents were observed in most PMC at MI, and the average chromosome configuration was 2n=44=21.82 II+0.36 I , and the chromosome configuration (2n=43=21 II +1 I) was observed in most PMC of F1 between Shannong87074-519 and C.S. at MI. Therefore, it was an alien disomic addition line with one pair chromosome of Elytrigia elongata. Then the St total genomic DNA was labeled as probe in GISH, the green-yellow hybridization signal was observed in two intact chromosomes, indicating that Shannong87074-519 was added by one pair chromosome of St genome. The SSR-PCR technique was employed in the primer filtration, and the molecular marker BARC165 was singled out from 170 primers, which could amplify the specific molecular marker BARC165(268) of Elytrigia elongata in Shannong87074-519. Subsequently, the specific segment in Elytrigia elongata was cloned and labeled as probe in GISH of root tip cells of Shannong87074-519, the light yellow hybridization signal was observed in both chromatin at interphase and chromosome at mitotic metaphase, thus the BARC165(268) could be applied as a specific molecular marker to detect alien chromatin of Elytrigia elongata in Shannong87074-519. Because of the good agronomic characteristics, high immunity to yellow rust, and dominant new yellow rust resistant gene located at the added chromosome St, assigned as YrSt temporarily, Shannong87074-519 has very important value in wheat breeding and genetics improvement.