Phase morphology and evolution during solidification process of polypropylene and poly(ethylene-co-octene) (PP/PEOc) blend in an internal mixer was investigated by means of scanning electron microscopy (SEM) and in-line back small-angle laser scattering (BSALS). The average particle diameter (d(p)) and the average characteristic length (L-m) were calculated by the pattern analysis of SEM micrographs to describe morphological variation with temperature during solidification process under the natural cooling condition. Furthermore, a fractal dimension (D-f) based on the probability density of the character length was calculated in this study to describe the distribution of main sizes of the dispersed phase particles. Structure parameters, such as heterogeneity distance (lc) and integral invariant (Q), were also calculated using BSALS to describe solidification process. The results obtained from BSALS were in agreement with those obtained from SEM, which means BSALS was valid to study the phase morphology and evolution during solidification process of polymer blend. POLYM. ENG. SCI., 51:609-616, 2011. (C) 2011 Society of Plastics Engineers