Morphologic characteristics of segmented block copolyetheramides based on nylon 6 and polyoxypropylene (POP) were investigated as a function of the compositions and block lengths of the hard and soft segments using small angle X-ray scattering (SAXS). Three POPs with different molecular weights were used as a soft segment. One-dimensional correlation functions were obtained from the desmeared intensity SAXS curves using the method developed by Vonk and Kortleve. The interdomain spacings were determined from the correlation distance at the peak position of the correlation function. From the dependence of the correlation distance on soft segment content, we deduced that an increase in the hard-segment length may lead to crystal formation by a chain-folding mechanism. The thickness of phase boundary was determined from the smeared intensity data using the method of Koberstein. A decrease in the phase boundary thickness with increasing soft-segment content suggests that an increase in the chain mobility by soft segment facilitates the regular arrangement of the hard segment, resulting in the formation of the hard domain with a narrow interfacial region.