Abstract: The experiments of solution culture and soil culture were conducted to screen the genotype of grain amaranth (Amranthus crenentus) in capability of enrichment in potassium, the content, uptake rate and uptake ratio of potassium in plant was used to the screening index of genotype of enrichment in potassium .The grain amaranths were cultured in low potassium solution for 30 days and in deficiency potassium soil for 60 days, the results showed that the species or cultivars of D8-1、R109、R104 and K12 had high capability of enrichment in potassium, the contents of potassium in plant were usually between 3% and 4%, the uptake rates of potassium in per plant were 50-75mg and 100-120mg, respectively, and the uptake ratios of potassium were over 1.70 mol/(gh), fresh root, the species or cultivars of D8-1、R109、R104 and K12 were called genotype of enrichment in potassium. However, the species or cultivars of M9 and Cr047 had low capability of enrichment in potassium, the contents of potassium in plant usually were below 2.7%, the uptake rates of potassium in per plant were below 40mg and 80mg, respectively, and the uptake ratios of potassium were below (1.30mol/(gh)), fresh root, which were called general genotype of uptake potassium. The differences of capability enrichment in potassium were very significant between different species of grain amaranths grown on deficient potassium soil after 60 days of seeding and in solution culture after 30 days of transplanting. The contents and uptake rates of potassium, which were between 2 and 5 times, 4 and 10 times, respectively than that in low potassium solution, were greatly increased in all species or cultivars, when the level of potassium was 5mmol/L in solution culture. However, the capability of enrichment in potassium was reduced with increase of potassium concentration in solution. Under the low potassium solution culture, the maximal contents and uptake rates of potassium were 2.5 and 2.3 times than the minimum in all experimental species respectively, and only 1.3 and 1.8 times in normal potassium solution culture. While, the ration of roots and shoots and the length of main root of two genotypes on deficient potassium soil were only half than that in low potassium solution culture. No matter what kinds of medium culture was used, ration of roots and shoots and the length of main root in genotype of enrichment in potassium were more than that of general genotype.