This paper analyzes three long duration heavy precipitation events in Liaoning Province using NCEP 1°×1° grid reanalysis data, FY-2E infrared 0.1°×0.1° TBB data and automatic weather station data.The relationship between TBB and precipitation and the characteristics and maintenance mechanism of mesoscale environmental field are studied.The conceptual forecasting model of long duration heavy precipitation in Liaoning is initially established.The results demonstrate that: When the pattern, location and intensity of subtropical high are conducive to heavy precipitation occurring in Liaoning, a favorable environmental background for the occurrence and maintenance of heavy precipitation is provided by the long-time interaction between the moist warm air transferred by low-level jet on the west side of subtropical high and the arid cold air on upper levels.There must be a continuous and stable water vapor transport before the occurrence of heavy rainfall, and there is no significant change in the intensity of water vapor transport and the thickness of wet layer in the process of heavy rainfall.The time length of strong vertical movement has good correspondence with the duration of heavy rainfall, and it is generally weak unstable stratification or neutral stratification on upper levels during heavy precipitation.The heavy precipitation can occur not only in the inner or edge of the cool cloud area of strong convective cloud but also in the warm cloud area where TBB value is small.TBB value is not necessarily related to precipitation intensity, but the rapid decrease of TBB value indicates imminent heavy rainfall.It is necessary to pay attention to water vapor transport, convergence and upward motion below 900 hPa in order to forecast location and intensity of precipitation in the warm cloud with low center of mass.These conclusions are helpful to deepen the understanding of the cause of long duration heavy precipitation in Liaoning area and provide clues for forecasting.