The purpose of this study is to evaluate of the safety and efficacy of decitabine treatment of Myelodysplastic Syndrome.

Total subjects: 240, doseⅠgroup of 120 patients, doseⅡgroup of 120 patients. Subjects are stratified randomize. If necessary, participants accepted best supportive therapy.

Inclusion Criteria:

• Age≥18;
• The diagnosis of MDS patients comply WHO2008 standards;
• IPSS score≥0.5;
• WHO classification for patients RCUD, RARS and transfusion-dependent RCMD;
• ECOG PS score: 0-2;
• Expected survival≥3 months;
• Serum bilirubin≤1.5*ULN, serum ALT and AST≤2.5*ULN, serum Cr≤1.5*ULN;
• Subjects signed informed consent form in line with GCP requirements.

Exclusion Criteria:

• Can not marrow biopsy;
• Previously diagnosed AML;
• Received azacitidine or decitabine treatment any time before;
• Being diagnosed with other malignancies in the prior 12 months;
• Pregnant or lactating women;
• Failure to control systemic fungal, bacterial or viral infection;
• Known or suspected allergy to decitabine;
• Known human immunodeficiency virus (HIV) or hepatitis B or C classes of active viral infection;
• Have a history of neurological or psychiatric disorders, including epilepsy or dementia;
• CTCAE 3 or 4 degree peripheral neuropathy;
• According to the investigator's judgment, there are concomitant diseases with a serious safety hazard or affect the patients completed the study in patients;
• Using other experimental drugs or participating in other clinical trials in the prior one months.