The invention discloses a method for manufacturing an optical fiber. The optical fiber comprises a fiber core layer and a cladding layer, wherein the cladding layer wraps the fiber core layer. The cladding layer is doped with fluorine and the fiber core layer is doped with F and Cl instead of Ge, wherein the doping concentrations of F and Cl are controlled at less than or equal to 50-500ppm; the cladding layer sequentially comprises an inner cladding layer, a depressed cladding layer and an outer cladding layer from inside to outside, wherein the depressed cladding layer is made of fluorine-doped substrate tubes and the outer cladding layer is made of fluorine-doped pure quartz sleeves. The fiber core layer and the inner cladding layer are prepared by fluorine-doped quartz tubes by virtue of a PCVD process in one time and then assembling with a low-refractive-index sleeve column and carrying out online RIC drawing. The fiber core layer is jointly doped with F and Cl; according to the cladding layer, C2F6 or SiF6 is adopted as a fluorine-doped starting material and subjected to gas-phase reaction on the inner wall of the fluorine-doped quartz tubes so as to deposit a fluorine-doped quartz layer and sequentially layer by layer form the inner cladding layer, the depressed cladding layer and the outer cladding layer.