Objective To investigate the clinical efficacy of tissue flap combined with antibiotic-loaded calcium sulfate and autogenous iliac bone grafting at stage Ⅰ for infected nonunion of long bone.Methods A retrospective case series study was conducted to analyze the clinical data of 51 patients with infected nonunion of long bones admitted to Tongde Hospital of Zhejiang Province from January 2013 to December2017.There were 42 males and nine females,aged 19-71 years,with an average age of 36.3 years.There were 43 patients with bone nonunion at tibia,six at femur,one at humerus,and one at ulna and radius.The range of bone defect area was 1-9 cm,with an average of 2.9 cm.On the basis of thorough debridement,tissue flaps combined with antibiotic-loaded calcium sulfate and autologous iliac bone graft were performed at stage Ⅰ treatment.The survival of skin flaps,infection control,nonunion healing and complications were recorded.Johner-Wruhs joint function assessment criteria were used to evaluate limb function.Results All patients were followed up for 10-35 months,with an average of 18.3 months.All flaps survived eventually.Except for one patient with infection recurrence,the other 50 patients with infection obtained primary cure.All nonunions were healed,with an average healing time of 6.4 months ranging from 4 to 15 months.Complications included venous crisis of skin flaps in five patients,anterolateral femoral cutaneous nerve injury in 20 patients,recurrence of infection in one patient,and infection of external fixator nail tract in three patients.Function evaluation results by Johner-Wruhs criteria were excellent in 34 patients,good in 14,and moderate in three patients,with an excellent and good rate of 94％.Conclusion On the basis of thorough debridement,tissue flap combined with antibiotic-loaded calcium sulfate and autogenous iliac bone graft can control the infection effectively,promote the bone union and improve the limb function.