The diurnal variations for carbonyl sulfide (COS) were measured during fall and winter seasons. All diurnal cycles except one day under strong wind showed characteristic diurnal variations for COS, with low values in daytime and high values at night. The vertical distribution of COS showed a significant gradient for COS among the three investigated heights; the mixing ratios of COS decreased while altitude increased. The high mixing ratios and distinct vertical distributions of COS indicate that strong sources of COS exist in Beijing City. Domestic stoves and central heaters are important sources of COS during winter season. Cesspools may play significant role on COS over whole seasons.