Kentucky bluegrass (Poa pratensis L.), a native grass species of the Qinghai-Tibetan Plateau, is widely used for ecological restoration due to its high growth rate and strong adaptability. However, monocultures of Poa pratensis are prone to rapid degradation and low productivity, limiting their suitability for animal husbandry. To address these challenges, this study evaluated the production performance and interspecific relationships of different mixed-sown and monoculture grasslands to identify optimal cultivation strategies. Field experiments were conducted over a six-year period, with three mixed-sown treatments-Poa pratensis combined with Siberian wildrye (Elymus sibiricus L.), Chinese fescue (Festuca sinensis Engler ex S.L.Lu), and alkali grass (Puccinellia tenuiflora (Griseb.) Scribn. & Merr.)-alongside their respective monocultures. LASSO regression (Least Absolute Shrinkage and Selection Operator Regression) and ROC curve analysis (Receiver Operating Characteristic Curve Analysis) were applied to identify key factors influencing production performance. The results indicated that the mixed-sown grassland of Elymus sibiricus and Poa pratensis significantly boosted forage yield by 216.88% to 323.06% in comparison with monoculture Poa pratensis. Additionally, the comprehensive evaluation index, which integrates forage yield and nutritional quality, was 16.41% higher for the Elymus sibiricus and Poa pratensis mixture than for the monoculture Poa pratensis grassland. These findings imply that the mixed-sown grassland of Elymus sibiricus and Poa pratensis effectively addresses the low productivity issue often seen in monoculture Poa pratensis grasslands. However, in terms of yield stability and interspecific compatibility, the mixed-sown grassland of Puccinellia tenuiflora and Poa pratensis demonstrated superior performance. Its relative total yield (RTY) consistently exceeded 1.0 from the third to the sixth year, reflecting higher interspecific compatibility and stable productivity over time. And the Poa pratensis and Puccinellia tenuiflora mixture showed the best performance, achieving the highest stability value of 3.12. Therefore, the combination of Poa pratensis and Puccinellia tenuiflora is recommended as the optimal strategy for achieving long-term yield stability and high productivity in cultivated grasslands.