The invention discloses a four-joint wagon. The four-joint wagon comprises a first wagon, a second wagon, a third wagon and a fourth wagon which are sequentially connected in series. Each of the firstwagon, the second wagon, the third wagon and the fourth wagon is supported by disc cores of two two-axis bogies, wherein lower core discs of the two two-axis bogies are matched with upper core discsof the wagons. Bodies of the first wagon, the second wagon, the third wagon and the fourth wagon only can rotate and cannot move transversely and longitudinally. The second wagon and the fourth wagonare main wagons, the first wagon and the third wagon are auxiliary wagons, and the two-axis bogies, close to the main wagon ends, of the auxiliary wagons can move transversely relative to the wagon bodies. The first wagon, the second wagon, the third wagon and the fourth wagon are hinged through hinges. The invention further relates to a connecting method of the four-joint wagon, the problems thatthe bogies are placed between the wagons in a joint wagon in the prior art, the finished wagon axle number is reduced, the baggage is increased, the wagon load is also limited, and the current transport capacity requirement is hard to met are solved.