The current study focuses on the electrolyte penetration of the graphite cathode in a NaF-KF-LiF-AlF₃ aluminum-electrolysis system with a cryolite ratio of 1.3. It involves a comprehensive investigation of the electrolyte in the cathode before and after electrolysis by X-ray diffraction and analysis of the results by semi-quantitative calculation in MAUD. The results show that KF can promote electrolyte penetration, with higher KF contents resulting in greater penetration. During electrolyte penetration, K₂NaAlF₆ and solid solutions containing KF play important roles in KF-containing systems. LiF effectively prevents the electrolyte penetration, while the Na₃Li₃Al₂F₁₂ phase plays an essential role in systems with high LiF contents.