Abstract: The issues of insufficient local mechanical performance and underutilization of materials caused by homogeneous filling in triply periodic minimal surface (TPMS) lattice structures are addressed. A coupled design method integrating topology optimization and principal stress guidance was proposed to enhance load-bearing capacity and functional adaptability. Gyroid, Primitive, and Diamond implicit surface models were first established, with compression experiments analyzing the anisotropic mechanical properties under different rotation angles. By employing topology optimization to guide density distribution and utilizing principal stresses to regulate unit cell type selection, a hybrid variable-density lattice structure with internal frame connections was constructed. The results demonstrated that the optimal model exhibited approximately 34% and 75% improvements in load-bearing capacity compared to reference models, respectively. This validates the effectiveness of the proposed optimization design methodology and internal frame connection approach.