With the merits of high energy density from lithium metal electrode and safety performance improved by inorganic electrolyte, all-solid-state batteries (ASSBs) are considered promising candidates for future lithium-ion batteries. However, dendrite growth induced battery short-circuit (SC) failure are the obstacles on the commercialization road of ASSBs. To unravel the dendrite growth mechanism, the electrochemical-mechanical coupled multiphysics model is developed from the cell level, based on which the dendrite mitigation strategy is further proposed by adding heterogeneous blocks (HBs) into solid electrolytes (SEs). It’s discovered that the electrochemical overpotential induced mechanical stress is capable of driving the crack propagation, which provides space for the dendrite growth to penetrate through the solid electrolyte, eventually causing the SC. Larger charging rate and smaller electrolyte conductivity results in earlier SC. Higher fracture toughness increases the cracking energy to suppress dendrite growth, while Young’s modulus affects both the driving force and resisting force for crack propagation. By adopting HBs in SEs, the dendrite growth behavior can be modulated. We discover that the length ratio between HB and SE dominates the dendrite mitigation effect. Single HB in large ratio, and multiple HBs in medium ratio with specific arrangement, are capable of completely suppressing dendrite growth-induced SC risk. Furthermore, multilayer SE in more layers and smaller Young’s modulus shows promising dendrite mitigation effect by delaying SC time. Results give out a comprehensive understanding of dendrite growth mechanism as well as an effective strategy to mitigate dendrite, providing guidance on the design of more robust and practical ASSBs with dendrite-suppression electrolyte.