[Objective] The effects of different irrigation methods and irrigation amounts on soil water, soil salt changes, and oat growth characteristics were explored to provide a scientific reference for improving crop production efficiency and soil water management in saline-alkali land. [Methods] Pot experiments were conducted with three irrigation treatments: conventional irrigation, fixed unilateral root-zone irrigation (FURI), and alternate partial root-zone irrigation (APRI). Three irrigation amounts were evaluated: W₁ (60% θ_f—70% θ_f, θ_f is field water-holding capacity), W₂ (70% θ_f—80% θ_f), and W₃ (80% θ_f—90% θ_f). Conventional irrigation was used as the control. Therefore, there were a total of nine treatment combinations. [Results] ① Under the different irrigation treatments, the change trend of water content in each soil layer was basically the same. As irrigation amount increased, the effect of salt leaching was more significant. The deep water content of conventional irrigation was generally higher than that of the other two irrigation treatments. ② Plant height, relative chlorophyll content of leaves, and oat quality increased with increasiong irrigation amount. The contents of crude fat, crude protein, and β-glucan in oat were 7.02%, 3.76%, and 6.06%, respectively, greater under the W₂ irrigation level than under the conventional irrigation level, but the SPAD values of oat leaves were lower under W₂, which affected the photosynthetic capacity of oat. ③ Soil salinity showed different degrees of accumulation as oat growth progressed, and the salt accumulation rate with alternate partial root-zone irrigation was the lowest. At the same time, soil salinity had a significant effect on oat root growth, water use efficiency, and yield. Total root length, total root surface area, and total root volume increased by 6.75%, 6.92%, and 12.5%, respectively. Water use efficiency increased by 17.32% compared with conventional irrigation with the same irrigation amount (W₂). [Conclusion] The medium irrigation amount (W₂) under alternate partial root-zone irrigation was beneficial for improving the production efficiency of oat and was better at controlling salt accumulation.