A series of segmented copolyesters with semi-regular structure was synthesized. In these copolymers, fully aromatic triad hard segments -HB-T-HB-, acting as mesogenic units, are linked each other by poly(ethylene terephthalate) (PET) segments with different average chain lengths as flexible spacers. The liquid crystallinity of the copolymers, i.e. the meso-phase forming ability, was studied against length of the spacer. In subsequent blending of these copolymers with PET matrix, results were compared with those from a commercial TLCP of PHB/PET random copolyester. Better mechanical properties were gained as expected since the compatibility of the segmented liquid crystalline copolyesters with the matrix is believed to be improved.