Abstract: This study aims to identify the optimal indices of the irrigation and nitrogen application in the high-quality and efficient peanut production under plastic-mulched drip irrigation. A two-year field experiment was conducted in Xinjiang, China. A systematic investigation was made on the responses of the peanut growth, yield, and quality to the water and nitrogen regulation. There were three irrigation levels (W₁, W₂, and W₃) and two nitrogen topdressing (N₁: half-reduced nitrogen; N₂: conventional nitrogen). The irrigation quotas were 22.5 and 30 mm (W₁), 30 and 37.5 mm (W₂), and 37.5 and 45 mm (W₃) in the 2022 and 2023 seasons, respectively. The conventional nitrogen topdressing rates (N₂) were 110.0 and 164.0 kg/hm² during the growing seasons of 2022 and 2023, respectively. A control treatment (CK) was included with no nitrogen topdressing under the W₂ irrigation level (W₂N₀). Entropy Weight Method for Order Preference by Similarity to Ideal Solution (EWM-TOPSIS) was employed to evaluate the optimal water-nitrogen combination. The overall benefits were then obtained, such as the pod yield, kernel quality, and water-nitrogen use efficiency. The results showed that there were significant effects of the irrigation and nitrogen application on the peanut growth indices, including the main stem height, leaf area index, and aboveground biomass. The W₃N₂ treatment consistently yielded the greatest main stem height (28.13 and 33.00 cm) across both growing seasons. While the W₁N₁ treatment was achieved in the smallest (15.50 and 21.50 cm). Compared with the CK treatment, the leaf area index increased by an average of 51.82% and 93.27% under the N₁ and N₂ levels, respectively, over the two years. Similarly, the aboveground dry matter increased by an average of 25.83% and 37.51% under N₁ and N₂, respectively. An irrigation range of 376.70 to 394.74 mm was found to impose moderate water stress. There was the "source-sink" relationship of the peanut plant. This stress promoted the plant growth, leaf functionality, leaf area index, and aboveground biomass. Consequently, there was an increase in the pod yield. The total seasonal water consumption of the peanuts ranged from 402.57 to 454.86 mm under high-yield conditions. The water consumption during the seedling, flowering, pod-setting, and pod-filling was accounted for 11.88%-17.62%, 28.36%-32.99%, 34.51%-43.81%, and 11.69%-21.95% of the total, respectively. Both stage-specific and total water consumption decreased with the increasing water stress at the identical nitrogen levels. There was no significant variation in the nitrogen application rate on the stage-specific or the total water consumption under identical irrigation levels. The water consumption percentages for the seedling, flowering, pod-setting, and pod-filling stages were 12.99%-18.00%, 26.10%-32.54%, 33.34%-43.25%, and 11.52%-24.21%, respectively. The flowering and the pod-setting stage were identified as the critical irrigation periods. Pod yield and water-nitrogen use efficiency exhibited an increasing trend with the higher irrigation amounts (up to 394.74 mm) and nitrogen application rates (up to 118 kg/hm²). By contrast, the pod yield declined when the irrigation exceeded approximately 502.29 mm. Moderate nitrogen application (≤ 118.0 kg/hm²) increased the peanut yield. While the excessive nitrogen application resulted in insignificant yield gains or even a decline. There was a significant interaction between water and nitrogen on the peanut kernel yield and quality. The EWM-TOPSIS evaluation showed that the optimal water-nitrogen combination was identified as a seasonal irrigation amount of 376.70 to 394.74 mm, with a nitrogen application rate of 110.0 to 118.0 kg/hm² (represented by W₃N₂ in 2022 and W₂N₁ in 2023). Compared with the CK treatment, this optimal combination increased the pod yield by 25.13% to 55.88%, kernel oil content by 1.27% to 3.56%, and water use efficiency by 26.74% to 44.44%. Furthermore, the superior performance of the W₂N₁ (2023) treatment was achieved over the W₃N₂ (2023). The pod yield increased by 9.59%, kernel oil content by 2.45%, irrigation water use efficiency by 25.00%, and partial factor productivity of nitrogen by 52.31%. An effective strategy of irrigation and nitrogen was recommended to simultaneously enhance the peanut yield and quality under plastic-mulched drip irrigation in the study area. These findings can also provide technical support to the green, efficient, and sustainable plastic-mulched drip irrigation in the peanut industry.