Elastomers with optimal mechanical performance and healability are indispensable for applications such as wearable electronics, automotive, and future robotics. Herein, an infrequent strategy was developed to build graft copolymer elastomers with polar polyacrylonitrile (PAN) as semicrystalline side chains and poly(methyl acrylate) (PMA) as amorphous backbones, in which the fraction of PAN segments and junction points was designed. Miniemulsion polymerization was utilized to increase the incorporation of semicrystalline macromonomers into amorphous backbones. The resultant graft copolymer elastomers (PMA-g-PAN) presented that the maximum toughness could reach 19.3 MJ/m(3). For PMA-g-PAN with a PAN content of 10.6 wt % and appropriate graft density (junction points of 10.1), the minimum residual strain was approximately 20% after the tenth stretch to 200% strain. The maximum residual strain runs up to approximately 70% after the tenth stretch to 400% strain. Results indicated that high toughness and excellent elasticity after cyclic stretching were assigned to the high molecular weight, optimized polar interaction between cyano groups, and crystallinity of side chains (PAN, 10.6 wt %) as well as the numerous junction points (10.1) of the graft copolymer. Additionally, elastomers in this work possessed excellent healability, and the healing efficiency was 82% under 50 degrees C only by interaction between cyano groups in side chains. In this work, we report a superior and convenient strategy for improving mechanical properties and prolonging the lifetime of polymeric elastomers only by importing polar and semicrystalline segments into the graft copolymer elastomer.