The invention discloses a single-mode coupling optical fiber with a low macrobend loss, comprising an inner core layer, an outer core layer, an inner cladding layer, a transition cladding layer, and an outer cladding layer from the inside to the outside. The outer core layer has a refractive index profile that is stepped from a refractive index of an inner core fiber to the refractive index of aninner cladding fiber. The transition cladding layer has the refractive index profile that is stepped from the inner cladding layer to the outer cladding layer. The refractive index of the core layer of the optical fiber of the invention is a stepped structure, so that a fiber material from the core layer to the cladding layer is linearly reduced by doping high concentration cerium, and the dopingin the core layer changes linearly rather than abruptly. The diameters of the inner cladding layer and the outer cladding layer are introduced into the transition cladding layer, so that an optical fiber material smoothly transitions from more fluorine doping to a pure quartz material, and the high parasitic loss caused by mutation of the material components in the heat treatment process is reduced.