When a typhoon approaches or lands at the southeast China coast. a heavy rainfall area usually occurs over mid-latitude China far away from the typhoon center. Especially when the typhoon is accompanied by a reverse trough extending northward, heavy rain fallarea is readily found in this inverted V-shaped trough. Energy-fronto-genesis is of ten observed with this trough. An attempt is made to explain the cause of the heavy rainfall through the kinematics ofenergy-frontogenesis. ω equation for saturated air and potential tendency equation are developed, incorporating the release of latentheat. Dynamic effect for energy-frontogenesis is analyzed by meansof the moist ω equation. Finally, as an example, the energy-frontogensis function for heavy precipitation process in the reverse trough accom-panying Typhoon 7504 is computed.