Background: Fibular allograft with impaction bone grafting (FAIBG) is an effective hip-preservation method for avoiding total hip arthroplasty in the early stage of femoral head necrosis. However, whether thorough debridement should be used with FAIBG is controversial. This study compared the mechanical performance between FAIBG with and without thorough debridement, which provides a biomechanical basis for selecting the proper treatment in clinical settings. Methods: Eighteen computational models were constructed and used to simulate two subtypes of femoral head collapse with seven debridement radii. The initial model was validated using the bony density distribution from X-ray images and a photograph of the cadaver bone cross-section. The stress of the anterolateral column and the debridement efficiency were computed and analyzed. Results: (1) The peak stress of the anterolateral column in all conditions could return to the physiological level, and in two cases, the decrement/increment of stress was almost less than 0.1 % when the debridement radius increased. (2) The load share ratio (LSR) of the cortical and cancellous bone was markedly decreased in the untreated condition and increases with an increase in the debridement radius. (3) A debridement radius greater than 1/2r yields a LSR value larger than that obtained in the normal condition. Conclusions: The simulation results provide specific biomechanical evidence to support the finding that FAIBG with a debridement region of 3/8 -1/2 appears to be a better choice for resisting femoral head collapse (FHC). Furthermore, FAIBG without thorough debridement, which requires relatively simple surgical devices and reduces artificial damage, appears to be a better method for resisting FHC than FAIBG with thorough debridement.