Abstract： In introduced the 4th edition(2008)of WHO classification of tumors of haematopoietic and lymphoid tissues.They are divided into 12 columns,which includes myeloproliferative neoplasms;myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDDFRA,PDDFRB or FGFR1;myelodysplastic/myeloproliferative neoplasms;myelodysplastic syndromes;acute myeloid leukemia(AML)and related precursor neoplasms;acute leukemia of ambiguous lineage;precursor lymphoid neoplasms;mature Bcell neoplasms;mature T-cell and NK-cell neoplasms;Hodgkin lymphoma;histocytic and dendritic cell neoplasms;post-transplant lymphoproliferative disorders(PTLD).Accroding to the progression of the molecular biology,the new classifications combines a lot of the new knowledge with gene, chromosome,immunophenotypes,morphology,histocytology et al.The chronic myeloproliferative disorders changes into myeloproliferative neoplasms(MPN),mastocytosis included in this column of MPN.There are three subdivisions in the column of myeloid and lymphoid neoplasms with eosinophilia and abnormalities of genes.Refractory anemia with ring sideroblasts associated with marked thrombocytosis(RARS-T)in the column of MDS/MPN.In the column of MDS,MDS in children is added.Myeloid sarcoma,Down syndrome with myeloid proliferation and blastic plasmacytoid dendritic cell neoplasm were added in the column of AML and related precursor neoplasms.Acute leukemia of ambiguous lineage includes 6 kinds neoplasms.Precursor lymphoid neoplasms (B & T cells)includes leukemias and lymphomas,the bone marrow lymphoblasts＞25% is defined as leukemia(no lower limit 20% as AML).Mature B-cell(39 neoplasms),T/NK cell neoplasms(22 neoplasms),Hodgkin lymphoma (6 neoplasms),histocytic and dendritic cell neoplasms (7 neoplasms).Post transplant lymphoproliferative disorders(PTLD)forms a new colunlns(5 neoplasms).