Effects of potassium (K) on root nutrimental ecology of winter wheat were studied on the National Purple Soil Fertility and Fertilizer Efficiency Monitored Base. The results showed that K application obviously increased K concentration in root, root length, root surface area, root activity, root dry weight, the amount of root in 40~100 cm soil layer and the ratio of root/ shoot. Significant correlation was found between the grain yield of winter wheat and root activity, root length, root surface area, root dry weight, root quantity in deeper soil layer. The correlation coefficients were 0.926^**, 0.865, 0.846,0.893^**, 0.996^**, respectively. These results suggested that the improvement of root nutrimental ecology had a positive effect on the grain yield of winter wheat.