DNA methyltransferase 3A (DNMT3A) is one of the critical epigenetic modifiers responsible for de novo DNA methylation. DNMT3A mutations are identified in some kinds of hematological malignancies, especially in acute myeloid leukemia (AML) with high frequency, indicating poor prognosis. Recent researches have shown that abnormalities of epigenetic related genes such as DNMT3A play important roles in the development and progression of hematological malignancies, which was named as class Ⅲ mutation associated with the pathogenesis of AML. In this review, the progresses of clinical and basic researches about DNMT3A mutation in hematological malignancies were summarized.