Context: In arid irrigated regions with limited growing seasons, establishing sustainable post-wheat (Triticum aestivum L.) cropping systems is crucial for agricultural intensification and soil conservation. Objective: This study aimed to evaluate and identify an optimal post-wheat cropping system that enhances biomass production, soil quality, crop performance, and economic returns under arid conditions. Methods: A seven-year field experiment (2018-2024) was conducted in northwestern China, comparing seven systems after spring wheat harvest: common vetch (Vicia sativa L.)/hairy vetch (Vicia villosa Roth.) mixture (WCVxHV), common vetch/rapeseed (Brassica napus L.) mixture (W-CVxR), hairy vetch/rapeseed mixture (WHVxR), sole common vetch (W-SCV), sole hairy vetch (W-SHV), sole rapeseed (W-SR), and a fallow control (WW). Results: The W-CVxHV system demonstrated exceptional performance. It produced the highest biomass, with increases of 14.3-23.9 % over other mixtures, and enhanced crude protein yield by 13.7-44.4 %. This advantage was supported by strong interspecific facilitation (LER=1.18). This system significantly improved subsequent wheat performance, increasing grain yield by 2.7-8.8 % and yield stability by 66.9 % compared to sole legume cropping. After seven years, W-CVxHV most substantially improved soil quality, increasing soil organic matter and total nitrogen while reducing pH, EC, and bulk density. Economically, the system achieved 9.8-14.1 % higher monetary value than other cropping systems. Conclusion: The legume-legume mixture of common vetch and hairy vetch represents a superior post-wheat cropping system, surpassing traditional fallow and single-species systems in agronomic, ecological, and economic performance. Implications: This system provides a sustainable alternative for integrated agricultural intensification in arid environments, contributing to soil health stabilization, yield resilience, and improved farm profitability.