Aerosol aging is the one of the research hotspots in the field of physical chemistry of atmospheric particulates at present. This study evaluates the impact of flyash in heterogenous reaction through the comparision of ozone oxidation reaction kinetics between the oleic acid (OA) thin film and oleic acid coated flyash which are observed by in situ vacuum FTIR for the first time. Except for the fingerprint region, the main bands of infrared spectrum of the fresh OA thin film and the fresh OA coated flyash are similar. When the two samples are exposed in the 20 ppm ozone concentration, room temperature and dry (RH~0%) conditions respectively, the CH absorption peak (3 050 cm-1) decreases while The —OH stretch band (3 430 cm-1) increases. Moreover, The carboxylic CO stretch band at 1 710 cm-1 decreases whereas a new ester group stretch band at 1 740 cm-1 appears and increases with increasing ozone exposure time. The OA component of the two samples can be gradually consumed and converted to some products containing hydroxyl and ester groups during the reactions through the changing trends of the infrared spectrum. The pseudo-first-order rate constant Kapp and the overall uptake coefficient γ, are obtained through changes in the absorbance of CO stretching bands at 1 740 cm-1. The ozonolysis reaction rate constant of OA coated flyash is nearly double to the OA thin film. Since the surface area-to-volume ratio of OA coated flyash is larger than the OA thin film and the ozone concentrations are the same for the both reactions, the γ values for ozone uptake on OA thin film and OA coated flyash are (2.70±0.11)×10-4 and (3.70±0.13)×10-4. Rapid reaction rate of the flyash sample is due to the larger catalytic surface area and more valid catalytic effect compared to the OA thin film. This demonstrates that the flyash often easily leads to the secondary organic aerosols (SOAs) when the flyash unites with unsaturated organic acids and exposes to the ozone oxidation environment.