Objective:To investigate the risk factors for chronic subdural hematoma(CSDH)recurrence and reoperation strategies in elderly patients.Methods:From October 2012 to December 2018, 56 patients aged 85 years and over with CSDHs undergoing surgery in our hospital were enrolled.After surgery, 12 patients had hematoma recurrence, of whom 11 received reoperation.The strategies of reoperation and the risk factors of recurrence were analyzed.Results:The average age was similar between patients with and without recurrence( t=0.308, P=0.759). However, the rates of recurrence between patients with mixed and with homogeneous density were significantly different(53.3% vs 12.8%, χ2=6.54, P=0.011), and there was also a significant difference in recurrent rate between patients with a small maximum thickness(1.0 cm to 2.5 cm)and those with a large maximum thickness(≥2.5 cm)before operation(12.5% vs 50.0%, χ2=4.753, P=0.029). Patients with a maximum thickness≥1.0 cm after surgery was associated with a comparable risk of hematoma recurrence compared with those with a thickness<1.0 cm(31.0% vs 12.0%, χ2=1.823, P=0.177). Most patients(10/11)achieved a good prognosis after reoperation. Conclusion:Reoperation can improve the quality of life in elderly patients with CSDH recurrence and without obvious contraindications.