Semicrystalline polymers products usually adopt a crystallized form in their end-use environment. These crystallized polymers undergo various deformations under different external fields (e.g., stretching) from precursor processing, post treatment to final shape formation. Such deformation process is accompanied by multi-scale and multi-stage structural evolutions due to the complex hierarchical structures of crystallized polymers. These structural evolutions control over essential physical properties of semicrystalline polymers, which can be further developed towards high-performance industrial materials. A profound understanding of associated mechanisms is the critical key to interpret the complicated deformation process and to optimize the practical performances of polymer materials. The past reviews have more or less focused on one aspect of deformation while the multi-scale vision is lacking. Herein, this review brings a comprehensive presentation of strain-induced structural mechanics of crystallized polymers based on a multi-scale, multi-stage standpoint from the initiation of plasticity until failure. Important structural changes and associated mechanisms during the whole deformation process are systematically summarized, with particular attention paid to the crystal phase transition and crystal morphology evolution. Besides, the relationships between resulted microstructures and the essential end-use properties of crystallized polymers as well as their performances as common industrial materials are discussed. By summarizing the recent processes, this review is hoped to open up more aventunes for developing deformation-inspired sophisticated materials facing broader and interdisciplinary application fields. Display omitted