We investigate a method to suppress the polarization-dependent loss (PDL) of long-period fiber gratings (LPFGs). We study the origins of the PDL and propose an azimuthally isotropic UV exposure to suppress the UV-induced birefringence and to realize low-PDL LPFGs. By using this technique and a low birefringent fiber together, the PDL of LPFGs can be reduced to a sufficiently low level required in high performance communication systems. Moreover, the validity of our theoretical modeling is confirmed by the experimental results.