Abstract: Soils contaminated with excessive combined heavy metals pose serious threats to ecological security and agricultural product quality; however, the remediation potential of monocotyledonous gramineous plants under such pollution conditions and their microbial synergistic mechanisms remain insufficiently studied. Soils were classified into three groups based on the single pollution index: Group A (P_i<30), Group B (P_iZn>30), and Group C (P_iCd>30). Perennial ryegrass (Lolium perenne L.) grown in these soils was selected as the test plant. By determining plant biomass and heavy metal bioconcentration factors (BCF), combined with 16S rRNA sequencing and PICRUSt2 functional prediction, the phytoremediation potential of ryegrass in contaminated soils and the underlying soil microbial mechanisms were evaluated. The results showed that ryegrass was able to grow normally in soils with ultra-high combined heavy metal contamination, with average biomass values of 5 627.50, 4 793.80, and 6 980.45 mg/plant in groups A, B, and C, respectively. Ryegrass exhibited enrichment capacity for multiple heavy metals, among which the BCF of Cd was greater than 1 in all three groups, reaching 3.01, 1.00, and 6.64 in groups A, B, and C, respectively, indicating that group C achieved the most pronounced remediation effect. Alpha diversity analysis revealed that the rhizosphere microbial diversity in groups B and C was significantly higher than that in group A (P<0.05). Both rhizosphere and non-rhizosphere soils were dominated by Ascomycota as the core microbial phylum, with relative abundances exceeding 40%. A total of nine differential microbial genera were identified in rhizosphere soils, while seven differential genera were detected in non-rhizosphere soils, all of which played important roles under high-level heavy metal contamination. PICRUSt2 functional prediction and KEGG annotation indicated that, in rhizosphere soils, three key functional enzymes were significantly and positively correlated with dominant microbial genera and were mainly involved in ion transport and carbon metabolism. In non-rhizosphere soils, eleven key functional enzymes showed significant positive correlations with dominant microbial genera and were primarily associated with organic matter degradation and energy metabolism. Overall, the results demonstrate that ryegrass exhibits strong phytoremediation potential in soils contaminated with ultra-high levels of combined heavy metals, and that soil microorganisms may exert synergistic effects through the regulation of functional enzymes.