in the present study, PC film of 0.125mm and 0.2 mm thickness were thermoformed into a cup shape by plug under a vaviety of processing condition, including mold temperature, film pre-heating temperature, plug depth, plug speed, and holding time, as well as multi-step thermoforming. their effects on the thermoforming film qualities were investigated. a grid was printed on the surface of the film before forming and then the dimension of the squared mark and the thickness of the formed film after forming were measured with the use of a precision imaging measuring system and thickness gauqe. the dimensional variation of the grid markings and the thickness distribution of the formed film give insight into the characteristics of the thermoforming. multi-step thermoforming was also applied to study its effect on the reduction of stress as well as warpage and wrinkling during the forming process. hopefully, knowledge of the effects of the processing parameters on the film forming will enable development of superioi films for later injection molding.