A thermotropic copolyester 1-19 prepared from a rigid, bent spirobicromane (SPI), 1,7-heptanediol (HD), and an aromatic eater triad, TOBC (terephthaloyl bis(4-oxybenzoyl chloride), was prepared and its thermal behavior investigated by differential scanning calorimetry. Copolyester 1-19 exhibited completely different DSC thermograms between samples cooled from the isotropic liquid and the mesomorphic states, a result attributable to the registry effect of the neighboring chains in the mesophase. Non-isothermal crystallization at different cooling/heating rates, and isothermal crystallization and annealing at various temperatures had been conducted to verify the origins of the complicated four melting endotherms (as T-m1, T-m2, T-m3 and T-m4 from high- to low-temperature regions) in the sample cooled from the mesomorphic state. The highest-temperature T-m1 transition is attributed to the melting of the primary crystal formed via the liquid crystalline nuclei. T-m2 and T-m3 transitions are due to melting of the less perfect, secondary crystals close and less close to the pure crystals responsible for the T-m1 transition. By choosing suitable isothermal crystallization and annealing processes, T-m2 and T-m3 transitions can be moved to merge with T-m1 to become one high-temperature single melting endotherm. The lowest-temperature T-m4 transition, which basically remained intact after different thermal treatments, is caused by the melting of the chain segments near the SPI moieties.