Leymus mollis (Trin.) Pilg. (2n = 4x = 28, NsNsXmXm) is a perennial tetraploid species in Leymus. L.mollis has excellent characters of strong and short stems, large spikes, multiple spikelets, high tolerance to drought, cold, alkaline and saline, as well as resistance to many fungal and bacterial diseases for common wheat improvement. Wheat and L.mollis was successfully crossbred, and a number of wheat-L.mollis derived lines were developed and identified by using morphological, disease resistance identification, cytology, GISH, FISH and molecular markers analysis. Three partial amphidiploids, M47 (2n = 8x = 56 = 42T.a + 14L.m, AABBDDNsNs) with large spike, high resistance to stripe rust, powdery mildew and FHB, M39 (2n = 56 = 44 T.a + 12 L.m, 1, 2, 3, 5, 6, 7Ns) and M42 (2n = 54 = 42 T.a + 12 L.m, 1-6Ns) with high resistance to stripe rust and FHB. Then, a series of disease resistance traits were introduced by hybridization of partial amphiploids with common wheat and durum wheat. Some derived materials had excellent characters of short stem, large spike, large grain and good quality, including 2 alien double additional lines 5Ns+6Ns, 6Ns+7Ns, six alien disomic addition lines 1Ns, 2Ns, 3Ns, 5Ns, 6Ns and 7Ns, two alien triple substitution lines 1Ns,5Ns,6Ns (1D,5D,6D) and 2Ns,6Ns,7Ns (2D,6D,7D), one double substitution line 2Ns,3Ns (2D,3D), six disomic substitution lines1Ns (1D), 2Ns (2D), 3Ns (3D),4Ns (4D), 6Ns (6D), 7Ns (7D), as well as five translocation lines. The resistance of stripe rust was related to 1Ns, 2Ns, 3Ns, 5Ns, 6Ns, and 7Ns chromosomes of L.mollis, among which 7Ns had broad-spectrum resistance, powdery mildew resistance was related to 7Ns chromosome of L.mollis, and FHB resistance was related to 2Ns, 3Ns, 4Ns, 6Ns, and 7Ns chromosomes of L.mollis. Many translocation types of new germplasm with excellent resistance have been obtained by 60Coγ irradiation. RNA-seq and SLAF-seq also has been used to develop some chromosomes specific markers of L.mollis, which will accelerate the identification and utilization of excellent genes. These excellent wheat-L.mollis derivatives will provide important germplasm resources to wheat genetic improvement.