Abstract: Three kinds of separation medium were used to prepare nuclear suspension of Triticum urartu. The preparation effect of Otto buffer was the best. Otto buffer was selected to prepare single cell suspension of 9 populations of Agropyron mongolicum Keng. The number of cells was counted by a microscope and its chromosome ploidy was detected by using flow cytometry （FCM） with T. urartu diploid as control. The results showed that the results detected by flow cytometry were consistent with the results by traditional chromosome preparation method and they were diploid.