Abstract: Objective To explore the effect of fludarabine on treatment of patients with chronic lymphocytic leukemia (CLL)and its influence on survival rate.Methods 32 elderly pa-tients with CLL were treated with fludarabine,and they were also divided into stage 0~Ⅱ (n =17)group and stage Ⅲ~Ⅳ (n =15)group according to clinical stage of disease.30 elderly pa-tients with medical examination were designed as control group.Number of peripheral blood lym-phocyte were compared between 3 groups,and the relationship between complete remission rate and the clinical related factors as well as survival rate within post-treatment 3 years in CLL pa-tients were observed.Results The number of CD4+ T cells in the control group was significantly higher than that in the stage Ⅲ~Ⅳ group (P <0.01).The number of CD4+ /CD8+ in the control group was significantly higher than that in the treatment group(P <0.05).There was a close rela-tionship between the complete remission rate of fludarabine treatment and the patient’s age,stag-ing and course of treatment.The survival rate within post-treatment 3 years was 65.6%.Con-clusion Fludarabine can significantly improve the patients′immune status and increase the com-plete remission rate and survival rate.