A fabrication method of multiwavelength fiber grating (FBG) was introduced in this paper.Using the scan exposure method, multiwavelength FBG can be successfully manufactured through applying different tensile force during multiple exposures process on the same fiber.Experiment results show that the position and the overlap of different sub FBGs will greatly affect the spectrum of every sub FBG.The spectrum of each sub FBG will be affected by short wave oscillation unless the length and position of all sub FBGs are fully overlapped.For hydrogen loaded fiber, the wavelength and reflectivity of the nth level FBG will increase as the (n+1)th level FBG is written.But for germanium doped photosensitive fiber, multiple exposures will increase the wavelength of previous sub FBGs while decrease the reflectivity of all sub FBGs.Through well distribute exposure intensity of every sub FBGs, a four wavelengths FBG with same sub FBG's spectrum is fabricated on a hydrogen loaded single mode fiber.