Based on the observational data and NCEP reanalysis data, the heavy rainfall event on 26—28 Aug 2004 in Shandong Province is diagnostically analyzed. The result shows that the event is caused by the interaction between 0418 tropical cyclone trough landed in Fujian Province and a weak cold front in the westerlies, it has obvious interacting characteristics between the two weather systems. The low-level southeast jet accompanying the tropical cyclone transports a plenty of heat and moisture for the event. It plays an important role in stimulating the convection that the weak cold air intrudes the area of the inverted trough, and conduce to warm frontogenesis, thus leading to the heavy storm. The heavy rain mainly distributed in the tongue area of high energy, the total energy is a key index to predict the rainfall area related to distant onland tropical cyclone.