Abstract: Different rice varieties have different responsibilities to various potassium concentrations. This paper reports a water culture experiment, conducted in 1985, with different potassium concentraions, giving prominence to the agronomic characters, the agrochemical and biochemical features as well as the sensitivity to low potassium concentrations. It makes a comparative study of the characteristics of rice varieties with degrees of tolerance of low potassium.Results showed that the rice varieties which were possessed of strong tolerance had remarkable adaptability to low potassium surroundings. They took up 30% more potassium than those which were not possessed of strong tolerance. Thus the above indexes in question of rice varieties. differing in tolerance showed significant diversity, esp. in the root system.Take Kefuhong No. 2 for example: its vitality of the root system, relative plant height above ground and relative biomass far surpassed those of the sensitive variety Xiulingxun. These results showed that the characters of tolerant varieties were closely related to the growth of the root system.