Background: Compound aluminum sulfate injection (CASI) originated from a Chinese traditional medicine, "Kuzhiye", and has been used in treating non-muscle invasive bladder cancer (NMIBC). Previous studies suggested that CASI was a potential monotherapeutic drug for NMIBC. However, the efficacy and safety of CASI in the treatment of NMIBC, as well as the long-term recurrence after treatment, need to be further evaluated. Methods: A multicenter retrospective single-arm cohort study was conducted. From 2006 to 2009, 101 patients (74 men and 27 women, aged 58.9 +/- 11.9 years) with T1 or benign NMIBC were enrolled. Each patient was directly injected with CASI through catheter needle into the root of NMIBC. Vital signs, electrocardiography, blood count, blood biochemistry, and urine analysis were re-examined on day 2 and day 14 after CASI injection, together with a cystoscopic examination 4 weeks after CASI treatment was performed for all patients to assess the clinical activity and safety of CASI. To study long-term efficacy, patients in center 2 were followed up for recurrence with a median follow-up time of 13.8 years. Results: For the 101 patients enrolled in this study, demographic characteristics in the 3 centers showed no significant differences. After CASI, 2 patients showed administration site-dependent, but not dose-dependent, increase in their aluminum concentration in 24 hours without obvious abnormality in blood biochemistry. The overall effective rate was 97.03%, including complete tumor necrosis in 94 patients. Treatment-related adverse events occurred in 20 patients (19.80%), including 9 drug-related and 11 cystoscopy-related Adverse Events (AEs). All AEs were endurable and disappeared within 2 weeks without any treatment. The maximum tolerated single dose of CASI was 21 mL. Among the 43 patients at center 2, 3 patients were excluded because they changed to other treatment regimen. As of April 2022, of the 40 patients enrolled, 22 had no recurrence and 7 relapsed. The follow-up time was 2-16.2 years. The other 11 patients were lost to follow up. Conclusions: CASI may be an effective and safe option for the treatment of NMIBC and is expected to be a potential monotherapy regimen for NMIBC.