Objective:To study the concentrations of fine particulate matters and ultrafine particles and influenced factors during winter in an area of Beijing .Methods:Real-time monitoring of particles ’ mass and number concentrations were conducted in an area of Beijing from February 7th to 27th , 2013.At the same time, the meteorological data were also collected from the Beijing meteorological website .Differences of the particles ’ mass and number concentrations during different periods were analyzed using Mann -Whitney U test.Meanwhile, the influenced factors were also analyzed .Results: The mean concentra-tions of fine particulate matters and ultrafine particles were ( 157.2 ±142.8 ) μg/m3 and (25 018 ± 9 309) particles/cm3, respectively.The particles’ number and mass concentrations in haze days were 1.27 times and 2.91 times higher than those in non-haze days, respectively.The mass concentrations of fine particulate matters in the self-monitoring site were higher than those in the nearest central monitoring sites, and the hourly-average concentrations of particles were significantly consistent with those at the commuter times.Meanwhile, the setting off of fireworks/firecrackers during the Spring Festival could lead to short-term increases of the particles ’ number and mass concentrations .When the wind speed was low and the related humidity was high , the concentrations of particulate matters were relatively high , and the mass concentrations of fine particulate matters were lagged about 1-2 d.Conclusion: The level of the particulate matters in this area was high .Heavy traffic , setting off of fireworks/firecrackers and meteoro-logical factors may be some of the main factors affecting the concentrations of the particulate matters in this area.Among those factors, the effect of setting off of fireworks/firecrackers didn’t last long and the effect of the meteorological factors had a hysteresis effect .