The invention provides a grating inscribing method, a grating inscribing device, an optical fiber and an optical fiber laser, and relates to the technical field of optical fiber manufacturing. The method comprises the following steps of: determining a specified medium doping diameter range for enabling the light power of a light beam in a specified mode in a model to be zero based on a corresponding relationship between the light power of the light beam in the specified mode in the laser model and a specified medium doping diameter in a fiber core of a fiber bragg grating; selecting a first diameter from the diameter range, taking a circle with the circle center of the cross section of the fiber core as a circle point and the diameter being the first diameter as a photosensitive lifting area, and taking other fiber core areas as compensation areas; and respectively carrying out specified medium doping on the photosensitive lifting area and the compensation areas based on different doping concentrations, and carrying out grating inscribing on the optical fiber doped with the specified medium. Non-uniform medium doping is carried out on the fiber core by setting the photosensitive lifting area, oscillation starting of a high-order mode in the laser can be restrained, and therefore, the light beam quality degradation and efficiency reduction caused by high-order mode oscillation are restrained.