Abstract: Objective: To evaluate the therapeutic efficacy of radioactive seeds on glioblastoma through interstitial irradiation. Methods: Nineteen patients with average age at 51.2 year old and diagnosed with glioblastoma for the first time participated in this study. All patients underwent micro-surgical operation to remove the tumor as complete as possible followed by routine post- operative radiotherapy with dose range at 42-54Gy. Among 19 patients, some were selected and received a total8 to 20 radioactive 125I seeds at mean dose 31.6Gy implantation on the tumor bed apart from eachother during the operation. The time of progression free survival (TTP) and overall survival (OS) of patients received surgery and post-operative radiotherapy comparing with the patients received additional 125I implantation during surgery was statistically analyzed. Results: The average TTP ofpatients with seeds implantation was 42.1± 2.4w (95%confidence interval was 37.2-46.5w) in contrast with 27.1± 2.7w (95%confidence interval was 24.3-31.8w) in control group. The average OS was 66.3±3.2w (95%confidence interval was 61.9-70.4w) for patients with implantation and 47.7± 2.6w (95%confidence interval was 44.4-50.5w) for patients without implantation. These data were statistically significant. Conclusion: 125I implantation during operation could rapidly reduce the tumor volume,limiting dose of radioactive seeding and exposure, so it provide more efficient therapeutic outcome and prolonged survival time. Because of small number of samples involved in this study, and inaccuracy during implantation which was performed under naked eyes, our data need to be further confirmed and evaluated.