Under deficient potassium soil culture and different potassium water culture, the changes of contents of different potassium forms were studied, which were in the soil of rhizosphere and non-rhizosphere in different grain amaranth genotypes. While the changes were investigated, which were in the quantities of microorganisms in rhizosphere, rates of important root exudates and H~ secretion and CEC of roots. The results were indicated that the content of available and slowly available potassium in rhizosphere was higher than that in non-rhizosphere, which formed a area enrichment in potassium comparatively in the rhizosphere. The ability of accumulated potassium in the enrichment genotype was significantly higher than in the common genotype. The content of total potassium of soil in rhizosphere was lower than in the non-rhizosphere , the decreasing extent of total potassium in enrichment genotype was higher than in the common genotype. Compared with the common genotype, the quantities of microorganism in rhizosphere and the exudation rates of main root exudates in enrichment genotype were higher significantly, while the changes of the quantities of bacterium and fungi in rhizosphere was same as the root exudates. CEC of root and the rates of H~ secretion in enrichment genotype were higher than in common genotype, but they were not significant difference in varieties of the same genotype.