A new method of fabricating all fiber broadband rejection filter based on long period fiber grating (LPFG) is proposed.The key principle of the method is to make periodic asymmetrical deformation in the core of fiber without microbends so that to induce periodic refractive index changes.Two ways to realize the asymmetrical fiber deformation are introduced and two kinds of filters whose rejection peak wavelength at 1 550 nm and 1 310 nm are obtained.The insertion loss is less then 0.8 dB and 1.4 dB respectively.The backward reflection loss is less than -70 dB.Such devices can be used as isolation filters in WDM systems.