The use of supplementary cementitious materials (SCMs) is an effective way to reduce CO2 emissions within the cement industry. In this paper, the Cement-Metakaolin (MK)-Sugarcane Bagasse ash (SCBA) ternary composite was designed based on the simplex centroid design method. The influence of MK and SCBA on mechanical properties of ternary composite was investigated. In addition, the hydration products and microstructure of ternary composite were analyzed by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), low-field nuclear magnetic resonance (LF-NMR). At the same time, the life cycle assessment (LCA) method was used to quantitatively analyze the environmental impact and economic cost of the ternary composite system. A multi-performance indicator was used to optimize the mix ratio of the ternary composite based on the simplex centroid design method, and it was concluded that the Cement: MK: SCBA ratio was 75%: 20%: 5% (by weight) to achieve the optimal synergistic effect. The findings of this study can offer a design methodology that considers both performance and environmental factors, while also providing a theoretical foundation for the utilization of SCBA in cement-based materials.