The liquid-liquid (L-L) phase separation and its effect on crystallization in polypropylene (PP)/ethylene-propylene-rubber (EPR) blend obtained by melt extrusion were investigated by time-resolved light scattering (TR-LS), optical microscope and small-angle X-ray scattering (SAXS). The existence of the lower critical solution temperature (LCST) was found by the kinetic analysis of the L-L phase separation, that is, the apparent diffusion coefficient of spinodal decomposition (SD), obtained by the TR-LS, decreased with increasing temperature. The L-L phase-separated specimen at 190 degrees C for various time periods was subjected to a temperature-drop to 130 degrees C for the isothermal crystallization and then investigated effect of L-L phase separation on crystallization. Memory of L-L phase separation via SD remained even after crystallization and crystallization proceeded only in PP-rich phases. The crystallization rate decreased with increasing L-L phase separated time at 190 degrees C. The rapid crystallization for short L-L phase-separated time could be ascribed to the elevation of chain mobility of PP by relatively higher amounts of EPR in PP-rich phases. The amount of EPR between PP lamellae in PP-rich phases was quantified using the correlation function, which is given by the fourier transform of the SAXS intensity.