Abstract: For the investigation of an arson fire, the case was largely classified with the flammable liquid residues detected at the fire scene. However, flammable liquid residues extracted from fire scence often had weathering effect, which hindered the identification of the flammable liquids and their residues. Flammable liquids and their combustion residues were used as the object, describing the weathering effect on changes in the substance of flammable liquids and their combustion residues at fire scenes and on their identification under different conditions (temperature and substrate), and the analytical methods of instrument and data were introduced to eliminate the weathering interference factors of flammable liquids and their residues. Some suggestions were given for the further identification of flammable liquids at fire scenes (44 ref. cited).