Objective To examine the efficacy and safety of 125Iseed implantation for treating neuroblastoma (NB) in animal models.Methods A total of 45 nude mice models of neuroblastoma were constructed and divided into the 125Igroup.control group.and blank group at 15 mice per group.The long and short diameters of the tumor were measured every 3 days.and the tumor inhibition rate was calculated every 9 days.Apoptotic and proliferative protein expression levels in tumor tissue and peritumoral tissue.as well as endocrine markers and bone marrow of the nude mice.were analyzed.The independent sample t test was used to compare the mean scores.and ANOVA was used for comparison between multiple groups.Results Tumor volume inhibition rate was significantly higher in the 125Igroup than in the control group and blank group on days 9.18.and 27(all P<0.05).Caspase-3 expression in tumor tissues was significantly higher in the 125Igroup than in the control group and blank group (all P<0.05).whereas proliferating cell nuclear antigen (PCNA) expression was significantly lower in the 125Igroup than in the control group and blank group (all P<0.05).There was no significant difference in Caspase-3 and PCNA expression between the control group and blank group (all P>0.05).In addition.no significant difference in the expression of Caspase-3 and PCNA in peritumoral tissue was observed between the 125Igroup.control group.and blank group (all P>0.05).Cell apoptosis in tumor tissue was significantly lower in the blank group and control group than in the 125Igroup (all P<0.05).while there was no significant difference between the blank group and the control group (P>0.05).There was no significant difference in endocrine markers between the three groups (P>0.05).There was no significant bone marrow suppression in the 125Igroup.and this observation was similar to those in the control group and blank group (all P>0.05).Conclusions 125Iseeds have significant toxicity to NB.125Iseed implantation is safe in nude mice with NB within the therapeutic doses.