Different from the basic sensing theory of the fiber Bragg grating (FBG) sensors based on spectral analysis, a new method utlizing the polarization dependent loss (PDL) of FBG for transversal pressure measurements is proposed. The evolution of the PDL with wavelength with respect to transversal pressure is studied theoretically and experimentally. A theoretical model for transversal pressure sensing by use of PDL is built and numerical simulation is also carried out. The theoretical analysis suggests that the PDL of FBG is more suitable for measuring transverse pressure than single spectral analysis in the low pressure region because of its greater sensitivity. Under the transverse pressure conditions of 0~180 N, the demodulation is realized by use of the centroid height and the wavelength spacing of the two peaks respectively. The resolutions of 0.06 dB/N for small pressure (0~80 N) and 2.5 pm/N for large pressure (81~180 N) are demonstrated. Good agreements between experimental results and numerical simulations verify the feasibility of the method.