<p>Electron avalanche breakdown plays a pivotal role in determining the efficiency and reliability of semiconductors and insulators in micro-nanoelectronics and power systems. However, it still remains challenging to understand and control this transient non-equilibrium process. Here, we propose and demonstrate an atomic-scale electron avalanche breakdown model to investigate the dynamic behaviors of excited electrons under extremely high electric fields in various dielectrics ranging from simple oxides to perovskites. Using high-throughput calculations, we establish the relationship maps between ionization energy, bond energy, electron mean free path and breakdown strength, and then excavate their mathematical expressions. On this basis, a high-entropy strategy in BaTiO₃-based dielectrics with controllable lattice distortion is well designed to regulate the electron avalanche process, which successfully achieves a ~ 250% improvement in the breakdown strength by preventing electrons from acquiring sufficient energy. The atomic-scale understanding of electron avalanche breakdown process provides more refined guidance for atom/defect engineering to break the universal rule of inverse relation between breakdown strength and permittivity in dielectrics.</p>