A new ring coupling structure for a linear accelerator includes an acceleration cavity, a coupling cavity, and a beam hole. The acceleration cavity and the coupling cavity are alternately assembled together. The beam hole penetrates through the acceleration cavity and the coupling cavity. The acceleration cavity adopts a bowl-shaped structure, a convex cone structure with a mesoporous is disposed on an inner wall of the acceleration cavity along the beam hole. Coupling holes between the acceleration cavity and the coupling cavity are designed as at least two waist-shaped holes uniformly distributed around the beam hole. The coupling cavity adopts a disc-shaped cavity structure with a thickened edge, and a nose cone is disposed in the coupling cavity and welded with cavity walls at both ends of a coupler. The left and right waveguide plates of the coupling cavity are welded together by using the nose cone.