To attain high humidity sensitivity, a sensitivity-enhanced sensor based on parallel fiber Fabry-Perot interferometers (FPIs) with the Vernier effect is proposed and experimentally demonstrated.It is made up of two optical fiber FPIs,each of which is based on a short capillary section with an inner diameter of 4 μm.A 2×2 coupler connects the two FPIs in parallel. The sensing element is one FPI covered with humidity-sensitive agarose film at its end face,whereas the reference element is the other.The theoretical study of the sensor′s operating principle and the experimental findings are in good agreement. Within the range of 40%RH—60%RH, high sensitivity of 0.843 9 nm/% RH is achieved.It is 44 times more sensitive than the direct tracing of a specific resonance dip in the superimposed reflection spectrum and is 9 times more sensitive than a single FPI.The thickness of the humidity- sensitive film is then increased,significantly improving the humidity sensitivity up to 1.12 nm/% RH.The easy fabrication,compact size,and high sensitivity of the proposed sensor indicate that it has a promising future in humidity detection.