There is a thin adhesive oil film between the floating oil seal lip and the shaft contact surface. The existence of this layer of oil film, on the one hand, can play the role of sealing the fluid medium, on the other hand, it can also play the role of lubrication between the lip and the shaft. However, during the use of the floating oil seal, due to the effect of the oil seal lip, the difference in the shaft surface and rotation conditions and the properties of the fluid seal, as well as the interaction and cooperation conditions of the three are often changed, so the floating oil seal often changes under dynamic conditions. It is a situation where fluid lubrication, boundary lubrication and dry friction coexist alternately. Therefore, a good seal can be achieved by ensuring that the thickness of the oil film is in an appropriate range.