The emissions of NO2 and HONO from the KNO3 photolysis in the presence of TiO2 were measured using a round-shape reactor coupled to a NOx analyzer.TiO2 played important roles in the emission flux density of NO2(RNO2)and HONO(RHONO),depending on crystal structures and mass ratios of TiO2.RNO2 and RHONO significantly decreased with increas-ing the rutile and anatase mass ratios from 0 to 8 and 0.5 wt.％,respectively.Nevertheless,with further increasing the anatase mass ratio to 8 wt.％,there was an increase in RNO2 and RHONO.RNO2 on KNO3/TiO2/SiO2 had positive correlation with the KNO3 mass(1-20 wt.％),ir-radiation intensity(80-400 W/m2)and temperature(278-308 K),while it had the maximum value at the relative humidity(RH)of 55％.RHONO on KNO3/TiO2/SiO2 slightly varied with the KNO3 mass and temperature,whereas it increased with the irradiation intensity and RH.In addition,the mechanism for NO2 and HONO emissions from the nitrates photolysis and atmospheric implications were discussed.