This study was aimed to evaluate the effectiveness and safety of low methylation drug decitabine combined with autologous cytokine induced killer cells (CIK) to treat the elderly patients with acute myeloid leukemia (AML). Two AML patients aged over 80 years old were diagnosed and treated in our department from 2006 to 2012; both company with MDS history, and one case was M4-type, another case was M6-type according to FAB classification. The changes in lymphocyte subsets, hematologic response, transfusion frequency, leukemic gene expression, obtaining CR or PR, quality of life and survival time of the patients with different treatment regimen (decitabine alone; CIK alone; decitabine combined with CIK) were systematically observed. The results showed that therapy of decitabine combined with CIK cells could reduce bone marrow suppression extent, decrease the frequency and volume of blood transfusion, and prolong the duration of partial remission, compared with the single use of CIK cell infusion and single use of decitabine treatment. Meanwhile, the kinds of expressed genes associated with leukemia decreased and the survival time was prolonged obviously. The patients' life quality significantly improved. It is concluded that decitabine combined with CIK for treatment of elderly patients with AML is safe and effective.