A relative humidity sensor based on two polarization maintaining fibers loop mirror with temperature compensation is presented. The proposed sensor is created through coating a thin layer of polyvinyl alcohol onto a polarization maintaining fiber from which a portion of the cladding is etched, and the other polarization mainting fiber is used to compensate temperature. The relative humidity optical fiber sensor which shows a linear response to parameter and compensates for temperature is tested with different surrounding humidity levels from 20% to 80%. Experimental results show that the sensitivity of the relative humidity measurement is 0.98 nm/% (RH) and the effect of temperature sensitivity is only 0.0072 nm/℃. The goal to offset the effect of temperature is experimentally achieved.