The wheat (Triticum aestivum L.) line 5R618 appears in low infection to most of Chinese current pathotypes of Puccinia triticina at seedling stage. In order to ascertain the resistance genes in 5R618, F2 segregating population and F2: 3 families originating from a cross between 5R618 and Zhengzhou 5389 (susceptible to leaf rust) were inoculated with pathotype THJP in greenhouse. The infection types were investigated 15 d after inoculation and molecular markers were also used for mapping the resistance genes. Results indicated that there was a single dominant resistance gene in 5R618, temporarily designated Lr5R. By using molecular marker Lr5R was located on chromosome 3DL and closely linked to barc71 and STS24-16, with genetic distances of 0.9 cM and 2.1 cM respectively. Based on the SSR markers, it can be concluded that Lr5R is likely to be a new leaf rust resistance gene.