A high-resolution transverse load fiber sensor based on microwave photonic filter (MPF) is proposed. It is different from the conventional fiber sensors based on spectral analysis because the signal demodulation is finished in the microwave domain. The working principle is as follows. With the polarization-maintaining fiber Bragg grating (PMFBG), a dual-wavelength ring fiber laser with a stable polarization is constructed. The microwave signal is modulated on the laser output and a MPF with two taps are formed with the time delay introduced by the long distance fiber. The theoretical and experimental results show that there exists a linear relationship between the frequency response of this filter and the transverse force on the PMFBG. The transverse force to be measured can be retrieved by the detection of the resonance frequency shift of this filter. In addition, in the experiment, a high sensitivity of 9.87 MHz·N -1 is obtained. The consistency between the experimental and theoretical results confirms the feasibility of this method.