1. Support the vehicle body, bear and transmit various loads and forces from the vehicle body to the wheel set or from the wheel rail to the vehicle body, and evenly distribute the axle load.2. The rolling of the wheel along the rail is transformed into the translation of the vehicle body running along the line through the bearing device.3. It can increase the load, length and volume of the vehicle and improve the running speed of the train.4. Ensure the safe operation of the vehicle, flexibly run along the straight line and smoothly pass through the curve.5. It has good damping characteristics, can alleviate the interaction between vehicle and line, reduce vibration and impact, reduce dynamic stress, and improve vehicle running stability and safety.6. Transfer the traction and braking force generated by the vehicle during operation to ensure that the vehicle stops within the specified distance.