Abstract: Background　Despite the clinical application of custom flange acetabular components (CFAC), the design of the pubic flange and the necessity of adjunctive screw fixation remain controversial, primarily due to a lack of relevant biomechanical evidence.Objective　The reconstruction of severe Paprosky type Ⅲ acetabular defects in revision total hip arthroplasty remains a significant challenge. Custom flange acetabular components (CFAC) have shown promising clinical outcomes in such cases. However, their biomechanical performance, particularly the role of pubic flange design and fixation in overall stability, remains unclear. This study aimed to compare the biomechanical differences between two CFAC designs under load using finite element analysis, providing a theoretical basis for clinical decision-making and prosthesis optimization. Methods　A three-dimensional pelvic model was reconstructed from CT data of a patient with a Paprosky type Ⅲ B acetabular defect and posterior column discontinuity. Two CFAC models were designed: a Dualflange construct without pubic flange fixation and a Triflange construct with pubic flange fixation. Finite element models were established using Abaqus software to simulate standing conditions. Peak stress and micromotion of the two prostheses and their fixation screws were evaluated and compared.Results　In both designs, peak stress was observed at the junction between the iliac flange and the acetabular shell. The Triflange prosthesis exhibited a peak stress of 39.46 MPa, approximately 25% lower than that of the Dualflange prosthesis (52.62 MPa). Peak screw stress in the Triflange group was 33.59 MPa, approximately 27% lower than that in the Dualflange group (45.71 MPa). Micromotion analysis showed that the screws at the acetabular roof and ischial flange demonstrated more pronounced micromotion compared to others.Conclusion　The addition of a pubic flange with fixation reduces peak stress and micromotion of both the CFAC prosthesis and its fixation screws. In complex acetabular defects of this type, pubic flange design and fixation may provide relevant clinical benefits.