The Polyaniline (PANI)@flower-like tungsten oxide (WO₃) nanocomposites with different mole percentages of flower-like WO₃(250%) were successfully synthesized by using a facile in situ chemical oxidation polymerization method and were loaded on flexible polyethylene terephthalate (PET) substrate to fabricate NH₃sensors operating at room temperature. The morphology, nanostructures and thermal degradation behavior of the as-obtained sensing materials were measured and characterized utilizing SEM, TEM, FTIR, XRD and TG. Gas-sensing performances of fabricated sensors were tested and results indicated that the sensor with PANI@10mol% flower-like WO₃exhibited the highest response value at approximately 20.1-100ppm NH₃at room temperature, which is more than 6 times higher than that of pure PANI. Notably, the lowest detection limit of 500ppb to NH₃was obtained at room temperature. Furthermore, the present sensor also showed rapid response and recovery rates of 13s and 49s, good repeatability, selectivity, and slight humidity effects to 10ppm NH₃at room temperature. Moreover, the gas sensing mechanisms of PANI and nanocomposites were also discussed in detail. The enhanced sensing characteristics of nanocomposites were related to the morphology structure and p-n heterojuction between PANI and flower-like WO₃.