This paper studied factors that affect consumers' feeling in fingers when unscrewing the cap to open an aluminum beverage bottle, and then investigated experimentally and numerically the size and surface shape of the cap in order to guarantee consumers' openability. Firstly, the gripping and opening way while rotating the cap by fingers was determined as the most popular opening way according to a survey of consumers. The grip force and torque were then measured simultaneously using an experimental bottle equipped with force sensors, and the relationships between the gripping force of fingers and the torque, the dimension and the gripping force of human hands were investigated. Moreover, experiments of semantic differential method were performed to study feelings in finger when pressing vertically and then moving along the surface of test pieces. It's observed that the dimensions of the surface in a wave-shape influenced the feeling in finger as well as the slip between the finger and the test piece. Finally, a finite element analysis model of finger pressing and moving along the wave-shape rigid surface was examined to evaluate numerically the discomfort and slip.