Abstract: The test selects white clover as male and caucasian clover as female F1 lines,different nitrogen and potassium treatment,to observe the root of different nitrogen and potassium responses for nitrogen and potassium for plant root growth.The results showed that root length,root diameter and root surface area were determined at the same time,found that parents and hybrids in the absorption of potassium ions may be affected by the nitrogen.When nitrogen level was N2 and N3 and K level for K2 and K3 treatment root indicators showed a maximum value.Under the interaction of nitrogen and potassium,F1 and parents showed that the indexes of root system were best under N3K2 treatment.