Segmented block ropolyetheresters based on poly(butylene terephthalate) and poly(tetramethylene ether glycol) with various hard segment contents were synthesized and four kinds of blends were prepared by melt blending these copolymer with each other by 1 : 1 blend ratio. The crystallization behavior of the component polymer of high hard segment content in the blends governed the overall crystallization in the blends. For all the samples examined there showed no sign of separate crystallization of the components and the component polymer of low hard segment content partly participated in the crystallization of the polymer of high hard segment content in blend. For the samples with the same hard segment content blends or copolymers, the blends always showed higher melting temperature than the copolymer, while the crystallinity or degree of phase separation between crystalline and amorphous phases in blend was always higher than that of copolymer.