Abstract: The concentrations of 13 kinds of carbonyl compounds in the ambient air in Beijing were measured by 2,4-dinitrophenylhydrazine(DNPH) and high performance liquid chromatography(HPLC),including routine monitoring once every 6 days,the hourly monitoring from 9:00 to 19:00 from May 26th to May 28th , 2020 ,where in Chegongzhuang which is an urban site; the synchronous monitoring three times a day from September 17th to September 21th, 2020 for Chegongzhuang and Yongledian site which is a boundary site of Beijing.Results were shown as follows,the total concentration of carbonyl compounds in the ambient air in Beijing was 25.1 μg/m³±8.5 μg/m³. The main components are formaldehyde, acetaldehyde and acetone, acetone > formaldehyde > acetaldehyde, in which acetone accounted for 43%, formaldehyde accounted for 31% and acetaldehyde accounted for 16%. Ozone generation potential (OFP) was formaldehyde > acetaldehyde > acetone, in which formaldehyde accounted for 66% and acetaldehyde accounted for 23%. In the seasonal variation,the total concentration of carbonyl compounds showed the characteristics of " summer > spring > autumn > winter" during 2020,which was mainly due to higher temperature,light intensity and more solvent evaporation emissions in summer than other seasons, at the same time gas particle partition coefficient of pollutants in summer is lower than in winter,the amount of carbonyl compounds transferred from the gas to the particle decreases accordingly.In the diurnal variation, formaldehyde and acetaldehyde showed "double peak" characteristics, the first peak appeared from 12:00 to 15:00, which was related to the enhancement of temperature and light, and the rate of photochemical reaction to produce aldehyde and ketone compounds was higher than the consumption.Formaldehyde and acetaldehyde mainly comed from the secondary photochemical reaction.The second peak appeared from17:00 to 19:00, which was related to motor vehicle emissions. Acetone is stable relatively and rises slightly at the traffic time in the afternoon, which was related to long atmospheric life and gradual accumulation. The data of May 29th indicated that carbonyl compounds are affected not only by light and motor vehicles, but also by meteorological factors such as temperature, humidity and wind speed.During the synchronous monitoring of Chegongzhuang and Yongledian in September, the concentrations of carbonyl compounds at the two stations were 24.4 μg/m³±7.8 μg/m³ and 24.1 μg/m³±7.5 μg/m³ respectively. The proportion of n-butyraldehyde and methacrolein at Chegongzhuang site is 4%, which is 2% lower than that of Yongledian site, it showed that Yongledian was more affected by industrial emissions compared to Chegongzhuang.The C1/C2 ratio in the ambient air in Beijing during the routine monitoring ranges from 0.8 to 3.6, and the C1/C2 ratios in spring, summer, autumn and winter were 1.9, 2.4, 1.7 and 1.2 respectively, the average value was 1.7. Consistent with the atmospheric proportion characteristics of typical large cities, the carbonyl compounds in the ambient air in Beijing also mainly come from human activities.