Background: Chronic myeloid leukemia is a clonal myeloproliferative neoplasm, characterized by the presence of chromosomal translocation t(9; 22)(q34; q11). This is found in over 95% of the cases and results in the BCR-ABL1 fusion protein with high tyrosine kinase activity. During the last decades, imatinib and other generations of tyrosine kinase inhibitor have been used effectively for target therapy of the disease. However, many of the drug resistant cases have been reported recently, due to the mutation within kinase domain of the BCR-ABL1 fusion gene. In order to provide further information about this incidence, we performed a retrospective study of 141 imatinib-resistance chronic myeloid leukemia patients to analyze kinase domain mutation by deep sequencing. Another group of 20 untreated patients were added as control.