The purpose of this study is to confirm the safety and the therapeutic effect of Decitabine in the treatment of elderly Acute Myeloid Leukemia (AML) patients.

The outcome of the elderly AML patients is very poor. No obvious progress was achieved in this field. Decitabine is a kind of specific DNA methylation shift enzyme inhibitor. It can reverse the DNA methylation and induce the differentiation and apoptosis of the tumor cells. Recent studies about decitabine in the treatment for elderly AML patients had achieved inspiring results and indicated that low dose decitabine maybe a good choice for elderly AML patients. So in this research the investigators plan to evaluate the safety and the therapeutic effect of decitabine in the treatment of elderly AML patients.

Inclusion Criteria:

1. Clinical diagnosis of acute myeloid leukemia.De novo or secondary AML.
2. Age >= 60years,female and male.
3. Before the enrollment，WBC < 40×10E9/L，Plt > 20×10E9/L（Hydroxyurea is permitted.）
4. In 2 weeks before the enrollment，total bilirubin < 1.5×ULN，ALT < 2.5×ULN；GGT < 2.5×ULN ，Scr < 2.0×ULN or creatinine clearance rate ≥ 50 ml/min（Cockroft-Gault）.
5. Before the enrollment，patients must be free from the toxicity caused by the former treatment.Received no chemotherapy in the last 4 weeks and no nitrosourea in the last 6 weeks.
6. Contraception must be taken to avoid pregnancy during the study.
7. ECOG 0,1, or 2, predicted lifetime longer than 12 weeks.
8. Patients must sign the informed consent prior to any study related screening procedures being performed.

Exclusion Criteria:

1. Acute promyelocytic leukemia.
2. Chromosome and genetic abnormalities related with t（8; 21）、inv（16）、t（15; 17）.
3. Central nervous system leukemia.
4. Bone marrow dry tap.
5. Patients received stem cell transplantation or chemotherapy containing azacitidine,cytarabine or decitabine in last one year, radiation therapy in last 14 days,lenalidomide in 30 days before included.
6. Patients suffered from autoimmune hemolytic anemia or immune thrombocytopenia.
7. Patients suffered from non-leukemia related comorbidities that will cause dysfunction of organs.
8. Patients suffered from unstable angina or （NYHA）3/4 Congestive heart failure.
9. Patients suffered from chronic respiratory disease and needed continued oxygen.
10. Other active malignancy.
11. Active HBV,HCV or AIDS patients.
12. Uncontrolled virus or bacterium infection.
13. The investigator believe that patients who are not suitable for this trial.
14. Severe mental or body disorders which will interfere the research such as uncontrolled heart,lung diseases,diabetes,etc.
15. Allergic to decitabine or its accessory.
16. Patients received other researches in last 30 days.
17. Without contraception.
18. Complications causing organ dysfunction which are not caused by AML.