The Hetao Irrigation District in the Inner Mongolia is one of the most important bases for commodity grains in China. However, there was a substantial reduction in the total water quantity diverted from the Yellow River. In order to alleviate the crisis of water shortage and promote agricultural watersaving in the irrigation district, a twoyear field experiment was conducted, in which five different threshold values of soil matric potentials (SMP) were set to trigger the mulched drip irrigation for spring maize, i.e., -10kPa (S1), -20kPa (S2), -30kPa (S3), -40kPa (S4) and -50kPa (S5). The soil water distribution, crop growth, and water use efficiency (WUE) were studied for the different treatments. The results showed that soil water contents varied significantly at different SMP threshold values during the two growing seasons of spring maize. The weighted averages of volumetric water content in the 0~60cm soil profile were increased significantly with the increase of SMP (p<0.05). When under lower SMP threshold values, plant height and leaf area index (LAI) of maize were relatively lower during the growing season. And premature senility of maize was observed when under the SMP threshold value of -50kPa. Aboveground biomass, hundredgrain weight and number of grains per spike were increased with the increase of SMP threshold values. When under higher SMP threshold values, higher maize yields were obtained. The yields of treatments of S1, S2 and S3 were significantly higher than those of S4 and S5 (p<0.05), but there were no significant difference among S1, S2 and S3. With the decrease of SMP threshold value, WUE was increased first and then decreased. The highest WUE value was obtained when under the SMP threshold value of -30kPa. Therefore, both taking into account the yield and WUE, it was recommended that the SMP value of -30kPa can be the threshold value to trigger mulched drip irrigation for spring maize production in the Hetao Irrigation District.