Objective To investigate the clinical significance of PD-L1 expression and its relationship with dynamic changes in the immune microenvironment in patients with recurrent or metastatic cervical cancer. Methods A total of 121 patients treated at the Department of Radiotherapy, Hebei North University Affiliated First Hospital, from January 2021 to December 2022, were enrolled. PD-L1 expression was assessed by immunohistochemistry (combined positive score, CPS), categorized as high (CPS ≥10) or low (CPS<10). Immune cell subsets (CD3+ T, CD4+ T, CD8+ T, CD56+ T, and Tregs) were quantified via flow cytometry at baseline, during treatment, and post-treatment. The primary endpoint was progression-free survival (PFS). Results PD-L1 high expression (CPS≥10) and low expression (CPS<10) rates were 35.54% and 64.46%, respectively. High PD-L1 expression was significantly associated with metastasis and HPV16/18 infection (P<0.05). PD-L1 high-expression group exhibited significantly higher proportions of CD3+ T cells (65.95% vs.62.25%), CD8+ T cells (28.26% vs. 24.56%), and Tregs (5.58% vs.4.48%) compared to the low-expression group at pre-treatment (P <0.001). With follow-up until December 2024, the high PD-L1 group demonstrated superior objective response rate (ORR: 60.47% vs. 38.46%, P=0.020) and median PFS (26 vs.18 months, P<0.001). Repeated measures ANOVA revealed that CD3+ T cells (F =107.3, P<0.000 1) and CD8+ T cells (F=407.7,P<0.000 1) significantly increased over time in the high-expression group, with notable interaction effects between PD-L1 status and time (P<0.05). Post-treatment CD8V+ T cell levels in the high-expression group significantly rose during and after therapy (P<0.000 1), whereas no significant changes were observed in the low-expression group. Tregs decreased over time (F=19.03, P<0.000 1), independent of PD-L1 expression. Multivariate Cox analysis identified low PD-L1 expression (HR=1.771, P<0.05) and metastasis (HR=1.770, P<0.05) as independent risk factors for PFS.Conclusion High PD-L1 expression correlates with enhanced CD8+ T cell infiltration and reduced Treg proportions, suggesting a more responsive immune microenvironment to PD-1 inhibitors, leading to improved short-term outcomes and prolonged PFS