Abstract: A method for suppressing supermode noise in all-polarization-maintaining actively mode-locked fiber lasers. A new reflective all-polarization-maintaining nonlinear polarization evolution (NPE) structure was designed, comprising a polarization maintaining fiber segment and a polarization maintaining fiber mirror. By adjusting the length deviation of the polarization maintaining fiber, the NPE operational curve can be controlled to achieve additive pulse limiting (APL) state. The peak power limiting effect in APL can suppress supermode noise. A 1.5 μm all-polarization-maintaining actively mode-locked fiber laser was constructed to experimentally validate this structure, with comparative analysis conducted on spectrum, pulse train, and radio-frequency (RF) spectrum before and after adding the structure. At 150th, 376th, and 602nd order harmonic mode-locking states, the supermode suppression level (SSL) of the laser could be improved by at least 23 dB compared to before noise suppression. The results indicate that the reflective NPE structure has good supermode noise suppression effect, with the advantages of low cost and simple structure.