The invention relates to the field of fiber communication, and particularly relates to an optical coupling structure and a plug in-type optical assembly. The optical coupling structure comprises a fiber and a first transmission medium, wherein the fiber has a front end surface with a certain included angle alpha with a surface vertical to a fiber axis direction and alpha is larger than 0 DEG; the first transmission medium is connected with the front end surface for coupling the light to the fiber via the front end surface; and the fiber is set in a bent or inclined mode in relative to incident light to enable the included angle theta between the incident light and the normal line of the front end surface to be larger than alpha. According to the optical coupling structure and the plug in-type optical assembly provided by the invention, through setting the fiber with the inclined front end surface with a preset inclined angle in a bent or inclined mode, the included angle between the incident light and the front end surface of the fiber is smaller, reflection of the incident light is further reduced, and as the fiber is set in a bent or inclined mode, the angle between the axial direction of an end section where the front end surface of the fiber is and refracted light entering the fiber is reduced, and the optical coupling efficiency is thus improved.