Karyotypes were studied via squash method in 5 Rosa laxa germplasm resources from Xinjiang. The results showed that ploidy levels were divided into diploid (2n = 2x=14) and tetraloid (2n=4x=28) . Asymmetry index ranged from 55. 14% to 60. 11%. The karyotypes of all the test materials were made of m and sm chromosomes,which include 1A,2A and IB. The results indicated that the existence of different ploidy levels is associated with the different regions and habitats where the germplasm resources grow. Karyotype of material No. 5 showed obvious difference with others,which was tetraloid,top asymmetry index and the most evolved karyotype. It was consistent with the previous view by Liu Shi-Xia that Rosa laxa var. Tomurensis S. H. Liou should be placed as a new variety of R. Laxa. While material No. 4 was regardedas another variety--R. Laxa var. Kaschgarica (Rupr. ) Han, which had already been approved by FloraXinjiangensis.%采用常规压片法,对从新疆采集的5份疏花蔷薇进行了核型分析.结果表明:疏花蔷薇包括二倍体(2n=2x=14)和四倍体(2n=4x=28)两种核型；核不对称系数为55.14％～60.11％;核型分类包括1A、2A、1B等3种类型；分析认为,不同倍性的出现与种质在不同区域、不同生境下生长有一定相关性.其中疏花蔷薇5号为四倍体,核型信息与其他材料差异明显,核不对称系数最大,核型分类也最进化.研究结果支持刘士侠等对其表型分类的划分,即托木尔蔷薇作为疏花蔷薇在新疆的特殊地理种；而4号材料也支持《新疆植物志》的分类,即建议喀什疏花蔷薇作为疏花蔷薇的变种.
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