This study was purposed to investigate the mutational status of DNA methyltransferase (DNMT3a) gene and the clinical features of AML patients with DNMT3a mutations. Using PCR combined with directly sequencing, the somatic mutations of DNMT3a involving residue of amino acid 882 were detected in 77 AML patients. Furthermore, the clinical features of these patients were also studied. The results showed that the DNMT3a mutation were detected in 7 out of 59 patients with de novo AML (11.9%), which included 4 patients with DNMT3a R882C, 2 patients with DNMT3a R882H and 1 patient with DNMT3a Y874C. Morphology examination indicated that 2 patients were M(2), 1 patient was M(4) and 4 patients were M(5). Cytogenetic analysis revealed that karyotype in 5 out of 7 patients with DNMT3a mutation were normal. In total of 27 patients with normal karyotype 5 patients (22.7%) were found harboring DNMT3a mutation, while no DNMT3a mutation was found in 21 patients with abnormal karyotype. The mutation rate in patients with positive CEBPA was obviously higher than that in patients with negative CEBPA (p = 0.002). Immunophenotype analysis showed that 4 patients (4/7, 57.1%) with DNMT3a mutation expressed lymphoid antigens including CD4 or/and CD7. There were no statistical significance in age, gender, blast cells of bone marrow, white blood cell and platelet counts, hemoglobin level, ratio of CR, mutations of FLT3-ITD, NPM1 and c-kit between patients with DNMT3a mutation and patients with wild DNMT3a (p > 0.05). It is concluded that the DNMT3a mutations are more prevalent in AML patients with normal karyotype accompanying with positive NPM1 and/or CEBPA mutation, the role of DNMT3a mutation in AML prognosis needs to be further studied.