The purpose 7f this study is to investigate the change of the ideal beauty of human bodies and the related clothing form designs from the ancient Egypt to the Romantic Period in the aspect of optical illusions effects to achieve the ideal beauty so that we can accumulate the knowledges for the modern clothing form design and the related optical illusion effects. The scope of this study is limited to the female body forms and female dress forms. The analysis on the optical illusions in the dress forms of the various period relied on the literatures and some representative photographs and figures. The important results are as follows : 1. In the body Priority type designs of Egypt, Greece and Rome, the natural Beauty of human bodies was represented by H type silhouett, the smooth and transparent drapery materials were used with radiant line pleats resulting in slant optical illusions. 2. In the clothing priority type designs of Byzantine, Gothic, Renaissance, Baroque, Rococo and Romantic Period, manteau, cotehardie, hennin and poulain were used to emphasize long arms and legs, high waists, belly curves and large heads resulting in optical illusions of vertical emphasize. Also long train, farthingale and panier were used to emphasize body expansion resulting in the optical illusions of Titchener alld Lipps. Large and complex patterns showed the optical illusions of Aubert. 3. In the clothing priority/body concealment type of Byzantine period, thick materials with precious gems and voluminous silhouettes were used to emphasize body expansion resulting in optical illusions of materials.