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To explore the dynamic response of root distribution and yield of summer maize to straw mulching under the optimized alternate irrigation of well-canal model, field experiments were conducted in Hetao Irrigated District in 2018 and 2019 under different tillage modes. The experiment consisted of four different treatments. It included conventional mulching (FM treatment), straw surface covering (BF treatment) and straw deep buried (SM treatment) under the irrigation mode of canal-well-canal, and the conventional mulching (CK treatment) under the irrigation of the whole canal. The results showed that the root distribution of summer maize under conventional tillage CK was shallow and wide, the root length density was decreased with the deepening of soil layer, and the root length concentration point was 0~20cm in the soil layer. Under the optimized alternate irrigation of well-canal model, the concentration point of the conventional mulching FM treatment of root length density was 10~30cm soil layer, which could not significantly improve the root length of the soil layer. Straw mulching significantly increased root length density, the root distribution of BF treatment was similar to CK, and the surface root length density was increased by 19.6% compared with that of CK. The root distribution of SM treatment was a deep and sticking type, and the root length concentration point was moved down to the 20~40cm soil layer. With the deepening of soil layer, root length density of SM was firstly increased and then decreased, which significantly increased the root length density of soil layer greater than 40cm, and it was increased by 91.7% compared with that of CK. The root length density in the horizontal direction of each treatments presented a standard normal distribution approximately centered on the plant, with a distribution radius of about 15cm. The optimized alternate irrigation of well-canal model significantly reduced water consumption and increased water use efficiency in the growth period of summer maize, but the yield of summer maize under FM and BF treatments was decreased by 10.1% and 1.3% on average compared with that of CK. The SM treatment had a better comprehensive effect, which increased summer maize yield by 8.9% and water use efficiency by 41.4% on average compared with CK. The research could provide some references for rational and safe utilization of brackish underground water resources, enriching the theoretical system of well-canal alternate irrigation, and saving water for agriculture and increasing crop yield in Hetao Irrigation District.