Piezoresistive strain sensor based on conductive polymer composites (CPCs) becomes more intriguing for great potential applications in recent decades. A trade-off relationship between “high sensitivity” and “high linearity and stretchability” in majority of strain sensors was shown. Large stretchability demands the material remains structurally and morphologically intact under strain, while high sensitivity requires substantial structural changes even under small strain. The conductive network morphology and interfacial interaction play the most important roles in determining the sensitivity of blended CPCs. In this research, incompatible ternary composites based on thermoplastic poly(ether)urethane(TPU) and Ethylene-octane block copolymer (OBC) and carbon black (CB) were produced with twin-screw extruder. Post-annealing was also conducted. The preferential distribution of CB in the blends, the conductive network morphology, the resistance variation of the as-prepared and annealed samples during static and dynamic tensile tests were investigated. The exponential revolution of resistive response to strain was also fitted with a model based on tunneling theory to investigate the change in tunneling distance and the number of conductive pathways. In summary, for TPU/CB or OBC/CB binary composites, similar three regimes of the resistance change ratio-strain relationship was shown. As for the strain range of different regimes and the strain sensitivity, especially in regime I, there is no significant difference. And the sensitivity in regime I is quite low. Lower percolation threshold value and monotonic variation relationship and higher sensitivity could be achieved through the construction of conductive network structure with CB selectively distributed in one polymer phase or the interface in TPU/OBC/CB ternary composites and post annealing treatment.