A new synthetic strategy for fiber grating was proposed. For a given reflection spectrum of a fiber Bragg grating, the index profile of fiber Bragg grating could be calculated by a layer peeling algorithm. Some superimposed fiber grating with different apodisation functions were used to fit this index profile. The special reflection spectrum of a fiber Bragg grating could be realized by controlling the superimposed fiber gratings parameters adjustment.The relative error between the reflection spectrum of synthetic superimposed fiber grating and the goal spectrum is less than 4.0%. It is a sample and quick method for fiber grating synthesis problems which is easy to implement.