Conjugated polymer P, which was synthesized by introducing 9,9-diphenylfluorene and thiophene units into the backbone of poly(fluorenylene ethynylene), showed high sensitivity in detecting nitroaromatics. A double-layer sensor, named P-PS/GEL, was prepared by electrospinning technique using polymer P, polystyrene (PS), and gelatin (GEL). A nanofibrous membrane from the mixture of PS and P as the top layer (P-PS) served as the sensing layer for detecting nitroaromatics (NACs). A gelatin nanofibrous membrane as the bottom layer (GEL) served as porous scaffold for the top layer. Therefore, apart from transferring into the top layer directly from above, the NACs molecules could also approach the top sensing layer through the bottom porous layer. This double-layer conformation greatly improved the permeability of the P-PS layer. As a result, the double-layer sensor exhibited a greater quenching efficiency (Q (f)) of 75 % than that of the single-layer P-PS (55 %). Importantly, the sensor showed good reversibility of quenching process after being exposed to saturated DNT vapor for 6 cycles.