Abstract: Objective To analyze the diagnosis course and treatment procedure of a patient with fever of unknown origin (FUO) by adopting case analysis combined with the plan-do-check-action (PDCA) cycle,which demonstrates the circuit diagram of diagnosis and treatment for FUO.The procedure and effectiveness of PDCA for FUO was evaluated by one case study. Methods The case study combined PDCA cycle was performed in one case of FUO to analyze the medical history materials,physical examination results,auxiliary examination reports and prevention of complications,and this FUO case was diagnosed as infective fever;then eliminating viruses and bacterial infections and it was suspected to be histoplasmosis or parasitic diseases;the marrow biopsy and blood rK39-Test confirmed it input Kala-azar;the therapeutic efficacy was predicted and complication was prevented based on analysis of previously literature,diagnostic criteria and therapeutic method. Results The case analysis combined with PDCA cycle improved the diagnosis of pathogenic causes and therapeutic effect of FUO. Conclusion The case analysis combined with PDCA cycle is helpful to improve the diagnosis and therapy level of FUO.