The invention discloses a low-loss optical fiber and a manufacturing method therefor. The optical fiber sequentially comprises a core layer and an adjacent cladding from the inside to the outside. The core layer does not contain germanium, and the content of fluorine in the core layer is less than or equal to 0.1wt%. The refractive index of the core layer is less than or equal to 0.05%, and the content of fluorine in the adjacent cladding is 1-2wt%. The refractive index of the adjacent cladding is less than or equal to 0.28%. The core layer and the adjacent cladding are doped with alkali metal halide. According to the invention, the attenuation caused by hydroxy radicals at the wavelength of 1383nm can be reduced in a process of rod shrinkage under the condition of meeting the requirements of the refractive index design of the core and cladding through adding the alkali metal halide. Meanwhile, the matching of the viscosity of the core layer and the viscosity of the cladding can be achieved through the optimization of the doping concentration of germanium, fluorine and potassium ions, thereby effectively reducing the fiber attenuation caused by the concentration of the stress of a fiber core in a wire drawing process.