The horizontal distributing characteristics of potential energy in three types of heavy rainfall are studied on the basis of energy synoptic principles. The heavy rain process on 11 August 1999 in Shandong Province is analyzed in aspects of horizontal and vertical potential energy and energy frontogenesis characteristics. The result shows that potential energy plays a good indicative role in heavy rain forecasting. The appearance of only high energy value does not mean heavy rainfall; but when the more powerful energy frontal zone and negative energy frontogenetical function zone move to the area and the convergence condition in the lower layer is favorable at the same time, severe precipitation is likely to occur. The heavy rain of August 1999 occurred at the front of the energy frontal zone, and the vertical distribution of potential energy can indicate the movement of cold air.