Traction pin for semi-trailer train and application thereof

The invention relates to a traction pin for a semi-trailer train and an application thereof. The traction pin for the semi-trailer train comprises an inner traction pin body (1) and an outer traction pin body (2), wherein the inner traction pin body (1) is used as a traction pin 2'' and the end surface of the bottom end of the inner traction pin body (1) is connected with a traction seat of a tractor in a contact manner; the outer traction pin body (2) is arranged on the inner traction pin body (1) and used as a traction pin 3.5''; through adoption of the inner traction pin body (1), connection between the traction pin 2'' of a trailer and the traction seat of the tractor is realized; and through adoption of the outer traction pin body (2), the connection between the traction pin 3.5'' of the trailer and the traction seat of the tractor is realized; therefore, the traction pin 2'' and the traction pin 3.5'' are singly used. Therefore, technical matching between the traction seat of the tractor and the tractio