Abstract: By analyzing the conventional observation data, sounding data and reanalysis data of NCEP/NCAR, the circulation background, boundary layer characteristics, dynamic conditions, thermal conditions and the airflow trajectory of the heavy haze in Jiangsu Province during autumn and winter of 2014 are discussed. The results show that zonal circulation at 500 hPa was of more straightly west or northwest airflow. The airflow at 500 hPa changed to the northwest can be an indicator that heavy haze will disappear in 6 to 12 hours later. The main surface situations were uniform pattern of pressure, cold front and inverted trough with low pressure. The surface situation changed when heavy haze occurrs. Just before cold front coming, the haze was heaviest. The east path of cold air was more effective for eliminating haze than the middle or western path. In most of the heavy haze days, the bottom of the temperature inversion was near the ground.Lower wind speed of less than 4 m/s was shown to be favorable for the development of haze. The daily variation was obvious with the haze mitigated in the afternoon. As the intensity and duration of temperature inversion are concerned, the inverted trough type was stronger than the cold front west path type, both of them were stronger than the uniform pressure type. But the three types were almost the same in terms of the thickness of inversion.Different types show different inversion intensity, which may be related to the prefrontal temperature enhancement and wind speed on 925 hPa and near ground, as well as air sources. The height of inversion layer is mostly under 300 m, with the intensity of temperature inversion for every hundred meters between 1 to 5℃, and higher relative humidity of greater than 40% and less than 90% were shown to be favorable for the development of haze. Underlying sink motion provided a favorable dynamic condition for haze, and, weak upward motion at 850 hPa was conducive to the upward development of haze. By using backward trajectory simulation, it is shown that the pollution for the uniform pressure type was mainly form the local emissions, cold front pollutants were from the northwestern or north China and transmitted over a long distance, and, the pollution for the type of inverted trough with low pressure mainly from the southern China. By studying the characteristics of heavy haze during autumn and winter of Jiangsu, meaningful results are obtained, which can provide more references for the future forecast.