Based on nationwide 63 data of nitrogen and phosphorus losses from 32 formally-published papers, the nitrogen and phosphorus loss ratios from agriculture in China were analyzed. The results showed a significant decline in N, P loss ratios values (p<0.05, n = 63) since 1990s. The changes in N and P losses from agricultural systems might be closely connected with widespread eutrophication nationwide. By linear regression analysis, we found that there is a good linear relationship between nitrogen and phosphorus loss ratios from agriculture and their impact factors, the regression equation is Y = -12.057 + 0.063X1 + 0.143X2 - 1.257X3 + 4.796 X4 - 11.060X5 (X1 : precipitation, X2: total nitrogen input, X3: total phosphorus input, X4: slope, X5, TN/TP, Y: N/P). However, there are still some defects in the quantitative model. The quantitative model is of important and realistic in strengthening water environment protection.