Developing new octoploid Trititrigia is of great significance for using Thinopyrum intermedium to the genetic improvement of common wheat. Ten octoploid Trititrigia accessions, i.e., Shannong TE256, Shannong TE259, Shannong TE261, Shannong TE262, Shannong TE263, Shannong TE265, Shannong TE266, Shannong TE267-1, Shannong TE270 and Shannong TE274, were developed from the progenies of the cross between Thinopyrum intermedium and common wheat variety ‘Yannong 15’. In this study, cytological methods and genomic in situ hybridization (GISH) were employed to determine cytological stability and chromosome constitutions of the 10 octoploid Trititrigia accessions. Mitotic observation indicated that most plants of octoploid Trititrigia had 56 chromosomes and a few had 54 or 55 chromosomes. Chromosomes in most pollen mother cells of plants with 2n = 56 formed 28 bivalents, showing a high degree of cytogenetic stability, simultaneously, univalents, trivalents and tetravalents appeared occasionally at meiotic metaphase I. At meiosis anaphase I (PMC AI), most chromosomes segregated equally to the two poles except for several univalent chromosomes moving ahead in very few cells. Fourteen Th. intermedium chromosomes were observed to be added to the whole set of common wheat chromosomes in each octoploid Trititrigia, and the alien chromosome constitutions of the 10 octoploid Trititrigia accessions were 2St+8JS+2J+2J-St, 2St+8JS+4J, 2St+8JS+2J+2J-St, 2St+8JS+2J+2J-St, 2St+8JS+2J+2J-St, 6St+4JS+2J+2J-St, 4St+6JS+2J+2J-St, 2St+8JS+4J, 2St+8JS+4J, and 4St+6JS+4J. These alien chromosome constitutions were different from those reported in octoploid Trititrigia, suggesting that the 10 octoploid Trititrigia accessions are novel materials and might be valuable in wheat breeding programs.