The controllable preparation of the phase separation structure of platic/elastomer blends is very important to improve the mechanical properties of materials. In this paper, polyamide 1212/hydrogenated nitrile (PA1212/HNBR) blends were prepared by melt-compounding method. During the mechanical testing, a novel viscoelastic–plastic transition behavior was observed. The addition of polyamide 1212 could effectively reinforce mechanical and frictional properties of HNBR matrix. It was worth noting that 30 wt% PA1212 content was the critical value of viscoelastic–plastic transition of the blends. Meanwhile, the tribological performance of the blends was also decayed at the critical point (i.e. 30 wt% PA1212). Therefore, the uniformly dispersed particle phase structure formed via Ostwald’s ripening mechanism was crucial to the improvement of tribological performance. In addition, the large-scale production of platic/elastomer blends with high-performance can be realized through this controllable preparation technique.