Blends of polypropylene (PP)/ethylene-octene copolymer (EOC) was studied. The influences of blend composition and processing conditions on phase morphology development of the blends were investigated by scanning electron microscopy (SEM) in detail. The minor composition formed the dispersed phase and the major composition formed the continuous phase, and the blends formed interpenetrating co-continuous morphology just at the intermediate concentration. The effect of concentration on phase coarsening was explained by the increase of dispersed phase coalescence with dispersed phase concentration's increase. Phase coarsening and phase fine dispersing were studied. The effect of mixing time on phase morphology development of the blends was investigated, the PP/EOC (80/20) blends has already formed a well-established droplet/matrix morphology after 1.5 min of mixing, and the similar blends phase morphology persisted until 11 min of mixing. The most prominent phenomenon is that the dispersed phase domain deformed from spherical droplet to elliptical droplet, even fibrillar or sheet morphology as the rotor speed increased. The increase of shear rate and elasticity ratio was applied to interpret this phenomenon.