Laser lights with different wavelengths were used to study the attenuation characteristics of fire smoke through considering the laser interaction with fire smoke and non fire aerosol at the same time.Three pairs of extinction coefficient ratio(ECR) for five kinds of typical fire smoke and non fire aerosol, including incense smoke and diesel flame smoke, etc., were obtained. It was shown that ECR reflects the relative extinction degree of lasers with two different wavelengths, so that ECR is only dependent on the basic characteristics of aerosols, irrespective of the concentration of aerosols. Different smoke aerosols will have evidently different ECR.