Objective To explore the treatment of acute promyelocytic leukemia (APL), and the management of retinoic acid syndrome (RAS) during treatment of APL. Methods On December 28, 2018, one case of APL patient with complex karyotype complicated by RAS who was admitted to the Hematological Disease Center of Lanzhou General Hospital, was selected as the subject. By retrospective analysis, the clinical data of this patient were collected, and the clinical manifestations, diagnosis and treatment process were analyzed. Induction chemotherapy of all-trans retinoic acid (ATRA) combined with arsenic trioxide (ATO) was used to treat APL: ATRA 20 mg/time, twice a day, oral, d1-28; ATO 10 mL/d, intravenous injection, d1-14. The RAS treatment regimen was to reduce or discontinue ATRA or ATO, and intravenous injected dexamethasone 10 mg/time, twice a day as soon as possible until hypoxemia is relieved. When patient′s white blood cell count (WBC)>10×109/L and continuously elevated, anthracycline or cytarabine was administrated as appropriate. The procedure followed in this study were in accordance with the requirements of the World Medical Association Declaration of Helsinki revised in 2013. And this patient signed the informed consents for clinical trials. Results On January 1, 2019, the patient was diagnosed as APL, with PML-RARα (Bcr1 type) positive, complex karyotype and intermediate risk group, based on complete results of relevant laboratory and auxiliary examination. This patient achieved good efficacy after treatment of ATRA+ ATO regimen. After treatment with ATRA, the patient presented fever, respiratory failure, pleural effusion, and increased WBC, etc.. Then RAS was considered. After treatment with dexamethasone, pirarubicin and symptomatic treatment, the patient′s clinical symptoms of RAS were significantly improved. As of February 2019, the patient was generally in good condition and was currently being followed up regularly. Conclusions ATRA+ ATO regimen has a good efficacy in treatment of APL. When RAS appears during the treatment, glucocorticoids and corresponding treatment should be actively used. Since only one patient was retrospectively analyzed in this study, the exact efficacy of APL and RAS needs further verification by expanding the study sample size. Key words: Leukemia, promyelocytic, acute; Tretinoin; Arsenicals; Acute promyelocytic leukemia; Retinoic acid syndrome; PML-RAR;ATRA; ATO; Dexamethasone; Retrospective studies