The effect of annealing and dynamic crystallization condition on the morphology and melting behavior of segmented block copolyethereslers based on poly(butylene terephthalate) (PBT) and poly(tetramethylene ether glycol) (PTMGT) was examined. The response of copolyetheresters to annealing was found to depend on the hard segment contents. The overall crystallinity BL increased with hard segment content. Upon annealing, Xc also increased for samples with high hard segment content, while it remained constant for samples with low hard segment content. It was explained from a viewpoint that crystallization during annealing was highly dependent on the crystallizable hard block length. The effect of dynamic crystallization condition on the phase structure of copolymer was also examined at the cooling rates of 7, 20, and 5$0^{circ}C$/min. For all the cooling rates examined both the overall and the hard segment crystallinity increased with hard segment content showing smaller values than those of annealed samples. The samples crystallized at 2$0^{circ}C$/min cooling rate always had higher crystallinity and lower amorphous fraction of hard segment than the samples crystallized under the cooling rates of 7 and 5$0^{circ}C$/min. This could be explained as a result of competition between a quasi-equilibrium crystallization profess and a kinetically controlled non-equilibrium crystallization process.