Polymer mechanochemistry on reactive species has attracted more and more attentions over the past 20 years, as the mechanochemical generation of reactive species has a great potential in developing different polymeric materials for various proposes, such as stress detection, self-healing, self-strengthening, controllable degradation and release of small molecules. In this review, we first discuss the recent progress on polymer mechanochemistry of the reactive species that are generated from the mechanochemical reactions of mechanophores. Five types of reactive species, including radical, zwitterion, ionic, carbene and neutral intermediates, and their applications were reviewed in detail. Since mechanochemical reactions are sensitive to the mechanophore structure and polymer framework, we then discuss how mechanophore isomerism, polymer structure, polymer attachment point, and polymer architecture influence the mechanophore activation. At last, we provide our perspectives on the polymer mechanochemistry of reactive species.