In this paper, a novel stiffness display device based on deformable length of elastic element control is presented firstly. The stiffness display device is composed of a thin elastic beam and an actuator to adjust the length of the beam. By controlling the beam length, the stiffness display device can reproduce the stiffness of the virtual object from very soft to hard, so that the human can feel it through fingertip as if he directly touches the virtual object by interacting with the device. Then experiments of human fingertip perception by using this device are carried out. The aims of the experiments are to explore the relations between human perception and differential thresholds, and get the characteristics of human fingertip, including force, times, frequency. At last, some important conclusions are drawn. The results can aid in the process of designing haptic devices.