A number of wholly aromatic copolyesters were prepared from methylhydroquinone diacetate, stilbenedicarboxylic acid, and at least one of the following diacids : isophthalic acid, terephthalic acid, and 4,4’-oxydibenzoic acid. The copolyesters were characterized by DSC, optical microscopy, and X-ray diffraction. The effects of composition on the thermal and structural characteristics of the materials were evaluated. Annealing after-treatments were also carried out. The results of different thermal treatments showed that copolyesters were substantially affected by thermal treatments in terms of both transition temperatures and structures.