Abstract: Objective To study the effect of repeated microwave hyperthermia inactivation on distal femur giant cell tumor. Methods Clinical data about 11 patients (7 males and 4 females) aged 19-42 years old (mean 27 years old) with distal femur giant cell tumor who underwent repeated microwave hyperthermia inactivation in our department from June 2006 to June 2012 were retrospectively analyzed.The effect of repeated microwave hyperthermia inactivation on repair of knee-cap defect with bone cement was assessed from the aspects of tumor reccurrence and knee joint function after operation. Results The patients were followed up for an average period of 26 months, during which the knee-cap was healed without fracture, internal fixation plate rupture, complication, deep infection, and distal metastasis.Local recurrence occurred in 1 patient 18 months after operation.Excellent and good functions of joints were achieved in 8 and 3 patients, respectively. Conclusion Combined in situ microwave hyperthermia inactivation and residual cavity microwave hyperthermia inactivation can effectively inactivate the residual cavity tumor and its adjacent foci, and repair the knee-cap defect with bone cement.The patients can carry out physical exercises with a heavy burden early after operation and shoten the course of treatment, thus improving their joint function.