To study the response of root distribution，physiological activity，yield and quality of maize to partial nitrogen replacement by organic fertilizer，the variety ‘Denghai 605’ was used in 2021 and 2022 in the dry area of southwest Shanxi province.Four organic fertilizer substituting chemical fertilizer nitrogen treatments were conducted，including local nitrogen application rate(210 kg·hm-2，N1)，15% nitrogen reduction combined with organic fertilizer(178.5 kg·hm-2，N2)，30% nitrogen reduction combined with organic fertilizer(147 kg·hm-2，N3)and 45% nitrogen reduction combined with organic fertilizer (115.5 kg·hm-2，N4).The amount of organic fertilizer used was calculated based on the substitution ratio.The soil water distribution，root growth characteristics，root physiological activities，yield and quality were measured during the growth period of maize.The relationship between soil moisture，root growth，root physiological activity and grain yield at harvest was studied under different organic replacement ratios.The results showed that the soil water content in 40-80 cm soil layer was increased by organic substitution，especially in N3 treatment.The soil water content in 40-60 cm soil layer was 11.3%-22.6% higher than that in other treatments.Organic substitution increased root length and root surface area in 0-40 cm soil layer，and root dry weight was increased by 6.4%-20.6%，compared with other treatments.Organic substitution also promoted water and fertilizer absorption and utilization by increasing root activity and nitrogen metabolism enzyme activity.The root surface area of 0-40 cm soil layer，the root activity of 20-60 cm soil layer and the activity of nitrogen metabolism enzymes had positive effects on yield.The grain yield，protein and starch content of N3 treatment were increased by 4.4%-9.3%，3.3%-12.7% and 7.4%-22.4%，respectively，compared with other treatments.Therefore，it is recommended to replace 30% inorganic nitrogen with organic fertilizer in dryland maize growing areas of southwest Shanxi province.It also could promote water and fertilizer absorption and utilization by improving root growth and root physiological activity，and improve grain yield and quality，which plays an important role in sustainable maize production in this area.