When an object is touched, the properties like shape, temperature, rigidity, texture and weight should be perceived. As a basic research of human tactile, it is most important to know how humans could perceive the shape of the object with fingers. Thus length and contacting curvature of an object are thought to provide important perception information. Most of the length perception studies are about two fingers using the thumb and the index finger. There are scarce perception studies using multi-fingers grasping. In present study, to investigate the human tactile length perception mechanism with multi-fingers, we develop a tactile length interface device for one and two lengths with three fingers and conduct two experiments of one and two lengths perception with three fingers grasping. The results showed that within the length range of 40 similar to 100mm, the one length perception was better than two lengths length perception and in two length perception, better perception took place when shorter lengths were presented to the thumb and the index finger compared to being presented to the thumb and the middle finger. As a result of force sensor, grip forces show no significant difference in the range of stimulating length.