Leaf spring is a suspension elastic element widely used in traditional automobiles. Its advantages are simple structure, reliable operation, low cost and easy maintenance. It is both the elastic element of the suspension and the guide device of the suspension. One end of it is articulated with the frame, which can transmit various forces and moments and determine the beating trajectory of the wheel. At the same time, it also has a certain friction and shock absorption effect. Killing three birds with one stone, it is widely used in non-independent suspensions.