Abstract: The characteristics of landfalling tropical cyclones are quite different. Some of them would quickly dissipate (0-24 hours, refer to STC) right after they made landfall while others would be sustainable over land for a longer period (3-5 days, refer to LTC) after they made landfall. Statistical analyses demonstrated that the severe calamities were closely related to those typhoons which were sustained over land for longer time period. Dynamical and diagnostic analyses were employed in this study with compositedat a of 7 cases of LTC and 7 cases of STC. The different characteristics of the large scale circulation for these two categories of landfalling tropical cyclones are found. The results have shown that the lower layer moisture channel connect with the tropical cyclone circulation or the landfalling tropical cyclones move to wards north and gain the baroclinic energy from the mid-latit udejet that were favorable to sustaining of a tropical cyclone over land. The vertical shear of the wind would be increased in this process. A landfalling tropical cyclone might be sustainable over land for a longer time if the upper levere envolope of the landfalling tropical cyclone linked with a mid-latit udejet to enhance the upper level out flow tow ards northeast or the cyclones moved. into an area under an upper level strong divergent field. On the ot her hand, friction dissipation effect of a ground surface would consume the energy of a landfalling tropical cyclone and results its decaying. The energ y budget calculation suggested that the long sustaining tropical cyclones would acquire Kinetic energy from the mid-latitude environment when they moved north ward approach the west erlies while short sustaining tropical cyclones would not gain the energ y from the environment. They would be dissipated by the frictional consuming. The results of this paper could help the operational forecast on the sustaining of a tropical cyclone over land after it made landfall.