Abstract-This article reports the effect of vapour chopping technique on the properties of vacuum evaporated poly (3-methyl thiophene) thin films such as surface morphology, optical transmittance, band gap, refractive index and optical transmission loss. Vapour chopping gives smooth surface morphology with smaller grain size reduced roughness than non chopped thin films, while the transmittance of the thin film increases with simultaneous decrease in the refractive index, band gap and optical transmission loss decreases due to vapour chopping.