Objective: To investigate the effectiveness of combiningtransurethral resection of bladder tumor (TURBT) with Bacille Calmette-Guerin (BCG) intravesical instillation in treating high-risk non-muscle invasive bladder cancer (HRNMIBC). Methods: We retrospectively reviewed the clinical data from 118 HRNMIBC patients treated at Tongren Hospital between March 2020 and June 2022. The patients were categorized into two groups based on theirtreatment regimen: the control group (n=60) which received regular pirarubicin intravesical instillation, and the observation group (n=58) which received additional BCG intravesical instillation alongside pirarubicin. All patients underwentTURBT. Postoperative follow-up included monitoring recurrence and adverse reactions. Quality of life was assessed for both groups before and after treatment. Peripheral blood T lymphocyte subsets and immunoglobulin levels were measured pre- and post-instillation. Patients were further classified into recurrence and non-recurrence groups to analyze factors influencing HRNMIBC recurrence. Results: The observation group exhibited a recurrence rate of 22.41% (13/58), notably lower than the 41.66% (25/60) in the control group (P<0.05). Both groups showed improved postoperative scores in somatic, emotional, social, cognitive, and role functions compared to preoperative scores, with the observation group demonstrating significantly higher scores across all domains (all P<0.05). Post-instillation, CD4+, CD4+/CD8+, Immunoglobulin M (IgM), Immunoglobulin G (IgG), and Immunoglobulin A (IgA) levels were elevated in both groups relative to pre-instillation levels, whereas CD8+ levels were reduced. The observation group showed significantly higher levels of CD4+, CD4+/CD8+, IgM, IgG, and IgA, and lower levels of CD8+ compared to the control group following instillation (all P<0.05). Univariate analysis revealed that tumor number, stage, grade, and primary tumor status were all significantly associated with HRNMIBC recurrence (all P<0.05). Multivariate logistic regression further identified tumor number, stage, grade, and primary status as independent predictors of HRNMIBC recurrence (all P<0.05). Conclusion: The combination of TURBT with pirarubicin and BCG intravesical instillation significantly lowers the recurrence rate in HRNMIBC patients and enhances both quality of life and immune function recovery. Independent factors affecting HRNMIBC recurrence include tumor number, stage, grade, and primary tumor status.