The responses of maize photosynthesis, yield and water use efficiency to different drip irrigation amount at different growth stages under full film mulching were investigated by a field experiment in the Hetao Irrigation District, China. The experiment consisted of 3 treatments, i.e. low (90 mm), medium (135 mm) and high (180 mm) drip irrigation amount with full film mulching, respectively. Except jointing stage, the maize leaf photosynthetic rate, transpiration rate and stomatal conductance under high and medium drip irrigation treatments were significantly higher than those under low drip irrigation (P＜0.05), while no significant differences were observed between high and medium drip irrigation treatments. Leaf water use efficiency (LWUE) under low drip irrigation was significantly higher than that under high drip irrigation (P＜0.05), and under high drip irrigation, LWUE at jointing stage was significantly higher than all other growth stages. The diurnal variations of maize leaf photosynthetic rates, transpiration rates, stomatal conductance and intercellular CO2 concentrations at different growth stages were found under all drip irrigation amounts. Photosynthesis range, peak height and peak time in the diurnal course with high and middle drip irrigation were significantly different from those with low drip irrigation. The survival rates, kernel number, 1000-grain weight and yield of maize with high and medium drip irrigation were significantly higher than those of low drip irrigation treatment (P＜0.05). The difference of high and medium drip irrigation treatments with full film mulching on the maize ear and yield was statistically insignificant, indicating that high drip irrigation amount was not necessary under full film mulching for the maize yield increase in the Hetao Irrigation District. This study could provide a theoretical basis for improving crop photosynthesis under drip irrigation in the Hetao Irrigation District, and thus enhance crop yield and water use efficiency.