Abstract: In order to observe the effect of BCG-PSN on cellular immune,fourty-five cases of breast cancer after surgery were treated with BCG-PSN in addition to routine treatment (Group A).They were compared with 25 cases who receive routine treatment alone (Group B).The result shows the ratio of lympho cyte subgroup CD4/CD8 gets higher in group A and remainds in group B.It suggests that BCG-PSN is able to activeate T lmphocyte subgroup and improne cellular immne.Therefore,BCG-PSN may be used a good auxilliary therapy for breast cancer patient.