The influence of oxidant on surface morphology and sensing property of polypyrrole (PPy) – poly (vinyl alcohol) (PVA) double layer sensors was investigated. PPy–PVA double layer sensors were prepared by vapor polymerization using FeCl3 as oxidizing agent and PVA as adhesive agent. The surface of PPy–PVA layer was observed on a scanning electron microscope (SEM). The surface morphology of sensor showed homogeneous layer and thickness of 1µm. And the sensing properties were investigated using a flow measuring system. The maximum sensitivity to methanol 1000ppm was proportional to increasing 12wt % FeCl3 concentration at 25°C. The response time was not affected by FeCl3 concentration, but the recovery time increased according to the amount of FeCl3. The best amount of FeCl3 was observed at 12wt%.