The crystallization process of poly(ethylene oxide) (PEG) and PEO/poly(methyl methacrylate) (PMMA) blends in the low molecular weight region of PEO was studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The half-time of the crystallization t(1/2), the time at which crystallinity X(t) = 1/2, was inversely proportional to the linear growth rate G of spherulite, i.e. t(1/2)(-1) proportional to G. The value of E characterizes the temperature dependence of the activation energy for the formation of a secondary nucleus on the growing side surface of the crystal lamella and was evaluated from the t(1/2) measured by DSC. The value of E of PEO was not affected by blending PMMA. However, the slightly increasing tendency of E was observed for PEO and PEO/PMMA blends with increasing molecular weight of PEO, M(PEO) This tendency may correspond to the crossover of E from low molecular weight material to polymer.