When the frame and the axle reciprocate relative to each other, and the piston in the shock absorber also reciprocates in the cylinder, the oil in the shock absorber housing will repeatedly pass through some narrow pores from an inner cavity. into another lumen. At this time, the friction between the hole wall and the oil and the internal friction of the liquid molecules form a damping force for the vibration, so that the vibration energy of the body and the frame is converted into heat energy, which is absorbed by the oil and the shock absorber shell, and then disperse into the atmosphere. The magnitude of the damping force of the shock absorber increases or decreases with the relative speed of the frame and the axle (or wheel), and is related to the viscosity of the oil. It is required that the viscosity of the oil used in the shock absorber is affected as little as possible by temperature changes; and it has properties such as anti-vaporization, anti-oxidation, and no corrosion to various metal and non-metal parts.