Abstract: Using “Bainong AK58” as experiment material, a field experiment was conducted to examine the effects of different concentrations of 5-aminolevulinic acid (ALA) (10 mg/L, 30 mg/L, 50 mg/L) applied at initial heading stage on leaf gas exchange and water use efficiency of winter wheat. The results were as follows: The stomatal conductance of winter wheat flag leaves treated with 10-50 mg/L ALA were significantly higher than that of the control (0 mg/L ALA); however the promotive effects of 10-50 mg/L ALA on stomatal conductance at flowering and milky stage was stronger than at dough stage. Applying 10-50 mg/L ALA increased the net photosynthesisrate of winter wheat flag leaves. At flowering and milky stage the increased net photosynthesis rate in 10-50 mg/L ALA treatment was mainly due to the decrease of stomatal limitation, while at dough stage it was mainly contributed to the decrease of nonstomatal limitation caused by decreased photosynthetic capacity of mesophyll cells. Compared with the control, 10-50 mg/L ALA had no significant effect on the leaf water use efficiency at flowering and milky stages, while increased the leaf water use efficiency significantly at dough stage. Applying ALA ranged form 10 to 50 mg/L increased grain numbers per spike, 1000 grains weight and grain yield of winter wheat. The highest grain yield was obtained when ALA was applied at level of 30 mg/L.