Objective To investigate the factors affecting the prognosis of patients with malignant obstructive jaundice(MOJ)after receiving biliary stent placement combined with intraluminal brachytherapy with 125I seed-strip implantation.Methods The clinical data of 52 patients with MOJ,who received biliary stent placement combined with intraluminal brachytherapy with 125I seed-strip implantation at the Jiangsu Provincial Cancer Hospital of China between January 2019 and January 2023,were retrospectively analyzed.The difference value between preoperative and postoperative number of lymphoid immune cells was recorded as△X.X-tile software was used to calculate the optimal cut-off value of △X,based on which the patients were divided into two groups.Univariate and multivariate analysis were used to determine the risk factors for overall survival(OS).Results The mean survival time of the 52 patients was(201.0±32.1)days.Univariate analysis indicated that postoperative TACE,preoperative ALT,preoperative AST,△lymphocyte cell,△CD3+T cell,△CD8+T cell,△natural killer cell(NK)and △regulatory cell(Treg)were significantly associated with OS,the differences were statistically significant(all P<0.05).Multivariate analysis revealed that △lymphocyte cell(P=0.007)and △Treg(P=0.038)were the independent risk factors for OS.Conclusion For MOJ patients whose△lymphocyte is ≥0.237 or △Treg is ≥0.21,a longer OS can be expected after receiving the treatment of biliary stent placement combined with intraluminal brachytherapy with 125I seed-strip implantation.