The aim of study is to explore the characteristics of cytogenetics and molecular biology in patients with eosinophilia. Bone marrow samples from 79 cases of eosinophilia (AEoC ≥ 1.5×10(9)/L) were detected for PDGFRA/B and FGFR1 gene rearrangement by fluorescence in situ hybridization and reverse transcription polymerase chain reaction (RT-PCR). Forty-four samples were detected for T cell receptor (TCR) clonal rearrangement by PCR. The results showed that among 76 cases the FIP1L1/PDGFRA (F/P) fusion gene was detected in 19 cases, the CHIC2 deletion was detected in 19 cases, the PDGFRA rearrangement was detected in 4 cases, and no FIP1L1 rearrangement was detected. According to the 2008 WHO classification, diagnosis were revised as myeloid neoplasms with PDGFRA/B rearrangement in 20 (42%) of 48 patients and 5 (83%) of 6 patients with hypereosinophilia syndrome (HES) or chronic eosinophilic leukemia (CEL), respectively. The diagnosis in (17%) of 6 patients with CEL was revised as chronic eosinophilic leukemia, not otherwise as specified (CEL-NOS). Clonal cytogenetic abnormalities were detected in 1 case of CEL-NOS and 3 cases with PDGFRB rearrangement. Karyotypic abnormalities involved in chromosome 4q12 were not detected in all of the 21 cases with PDGFRA rearrangement. The clonal TCR gene rearrangement were detected in 33% (5/15), 40% (6/15), and 36% (5/14) cases with PDGFRA/B rearrangement, HES, or secondary eosinophilia, respectively. There was no statistical difference in incidence rate among 3 subgroups. It is concluded that PDGFRA/B rearrangement can be detected in many cases of HES or CEL. Interphase FISH and PCR testing can enhance the diagnostic rate of myeloid neoplasms with PDGFRA/B rearrangement.