Abstract: Total knee replacement has become a viable option for treating severe knee arthritis. The demand for more kinematically functional implants that better replicate natural knee kinematics led to the development of total knee arthroplasty (TKA), including bi-cruciate-retaining (BCR) TKA. However, optimised design parameters of BCR TKA knee implants that can help achieve a long-term prosthetic survival rate remain unknown. Therefore, this study aimed to investigate the effect of the design parameters of BCR TKA knee implants on the mechanics of knee joints and optimise and individualise the knee implant design parameters using the Taguchi method incorporating finite element analysis. Herein, experimental factors and levels were selected and nine finite element models of BCR TKA knee implants were developed to optimise the design of the following parameters: the curvature ratio on the sagittal plane, curvature ratio on the coronal plane, and tibial slope. In addition, finite element analysis was used to determine the effect of the design parameters on the peak contact stress on ultra-high-molecular-weight polyethylene (UHMWPE) and its deformation. Consequently, among the three parameters that affect the peak contact stress and its deformation, the curvature ratio on the sagittal plane had the greatest effect (range = 10.96), followed by the curvature ratio on the coronal plane (range = 3.54), and the tibial slope (range = 2.56). The optimal design parameters for the BCR TKA knee implant were a curvature ratio of 1.5 on both the sagittal and coronal planes and a tibial slope of 5°. Under these conditions, the peak contact stress and deformation were 25.80 MPa and 0.0835 mm, respectively. The optimisation method based on finite element analysis and the Taguchi method can produce one of the highest-performing BCR TKA knee implant designs, thereby reducing the peak contact stress and deformation. This method sheds fresh light on the development of the BCR TKA knee implant as well as biomechanical decision-making to implant the TKA prosthesis correctly.