Segmented block copolyetheresters based on poly(butylene terephthalate) and poly(tetramethylene ether glycol) with various hard segment contents(HSC) were synthesized and flour kinds of blends were prepared by melt blending these copolymers with each other by 1 : 1 blend ratio. The investigation of the effect of annealing on the crystallization of the solid samples confirmed the previous supposition that crystallization behavior of high HSC polymer governed the overall crystallization in the blends and the low HSC polymer participated in the crystallization of the high HSC crystal as a form of secondary crystallization. The amount of secondary crystallization due to hard segments of the low HSC component polymer which were confined to the main crystal increased with the cooling rate. The crystallization rate of the blend was always greater than those of the component polymers. For the blend and copolymer samples with the similar HSC, the blends always showed higher crystallization rate. The effect of hard segment length distribution on the crystallization rate was also discussed.