Sensitivity is one of the important performances for sensor. Without increasing system complexity, this paper studied the influence of self-performance and polarization maintaining fiber(PMF) length on the axial strain sensitivity of polarization maintaining loop mirror(PM-FLM)based on the theoretical model of PM-FLM by numerical simulation and experiments. The results show that we can choose a long wavelength point as a monitoring point to optimize the axial strain sensitivity for the same PM-FLM, a high strain dependent birefringence coefficient PMF to optimize the axial strain sensitivity for the PM-FLM with the same birefringence, a low birefringence PMF to optimize the axial strain sensitivity for the PM-FLM with the same strain dependent birefringence coefficient and the axial strain sensitivity is unrelated to PMF length.