Objective By literature review to retrospectively study the diagnosis and treatment process of decitabine combined with ruxolitinib in treatment of elderly patient with atypical chronic myeloid leukemia (aCML) for improving the understanding of aCML. Methods To report a case data of elderly aCML patients with CSF3R T618I mutation and the clinical treatment process using decitabine combined with ruxolitinib. Search CNKI, Wanfang data knowledge service platform, PubMed database (as of December 2021). Combined with literature reports to summarize the clinical characteristics of aCML and the effectiveness and safety in treatment applying decitabine combined with ruxolitinib. Results A case of 72-year-old man, admitted to our hospital since fatigue and dizziness for more than 1 month, and diagnosed as aCML with obviously increased white blood cells, granulocytic proliferation and granulocytic dysplasia with primitive cells <20%, and CSF3R T618I mutation detected by next-generation sequencing (NGS) analysis. After targeted therapy with ruxolitinib and 4 courses of treatment with decitabine, the patient achieved complete remission (CR) on morphology and had a good response on molecular. The patient's primary disease remained stable by maintenance therapy with ruxolitinib. A total of 11 cases treated with hypomethylating agents such as decitabine and azacitidine in aCML were found in literature, including 8 cases treated with decitabine alone [the CR rate was 87.5%(7/8)],2 cases treated with azacitidine alone [the effective rate was 50.0%(1/2)], and 1 case treated with decitabine combined with CAG(recombinant human granulocyte colony-stimulating factor + cytarabine + aclacinomycin) chemotherapy and achieved CR. A total of 4 cases treated with ruxolitinib alone in CSF3R T618I mutant aCML were found in literature and the overall efficiency was 50.0%(2/4). No case treated with drug combination in treatment of decitabine and ruxolitinib were found by searching literature. Conclusion aCML is a kind of rare disease, the diagnosis is based on morphological grounds only. The drug combination of decitabine and ruxolitinib is effective and well tolerable in this elderly patient with aCML.