Salinity increasingly limits crop productivity in arid regions. Legume-rice rotations improve soil fertility, the impact of rotation duration on soil health, ecosystem multifunctionality (EMF), and yield interactions remains unclear. We compared plots after 1, 3, 5, 8 and 10year rice monocultures rotation soybean (R1D1-R10D1), focusing on soil quality index (SQI), enzyme activities, EMF, and yield. The results indicated that R5D1 significantly improved soil quality, increasing SQI by 88-477% compared to other treatments. Specifically, R5D1 enhanced soil organic carbon (SOC), available phosphorus (AP), and available nitrogen (AN), while reducing EC and pH. These improvements in soil physicochemical properties fostered greater microbial diversity and abundance, thereby elevating EMF by 51-1486%. Furthermore, R5D1 improved soybean yield by 144% compared to R3D1 (p < 0.05), and achieved yields comparable to or slightly higher than those of longer rotations maintaining parity with longer rotations (R8D1 and R10D1). These benefits were attributed to integrated improvements in pH, SOC, available nutrients, and microbial communities. Consequently, a 5-8-year rice-soybean rotation optimally enhances EMF and yield on saline alkali land.