| Based on quadratic regression orthogonal design of four factors method, This study established a quadratic polynomial regressionmodel for major agronomic practices of spring wheat in Inner Mongolia Hetao irrigation district. The results showed that effects of four agronomic measures on yield were in the order of sowing density＞amount of phosphorus fertilizer＞nitrogen rate＞irrigation quantity, and those on water use efficiency were irrigation quantity＞sowing density＞nitrogen rate>amount of phosphorus fertilizer. The optimizing combination agronomic measures for spring wheat in Hetao irrigation district are proposed as follows: seedling density 6.675～7.171×104 plants·hm-2, phosphorus rate (P2O5) 147.0～175.5 kg·hm-2, nitrogen rate (pure N) of jointing stage 164.5～186.6 kg·hm-2, irrigation amount at jointing and heading stage 909.7～963.0 m3·hm-2. Collectively, these combined measures can achieve the target yield of spring wheat over 7 500 kg·hm-2 and water use efficiency above 1.6 kg·m-3. |